MERCK & CO INC
10-K/A, 1999-06-11
PHARMACEUTICAL PREPARATIONS
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<PAGE>   1

     AS FILED WITH THE SECURITIES AND EXCHANGE COMMISSION ON JUNE 11, 1999
- --------------------------------------------------------------------------------
- --------------------------------------------------------------------------------

                       SECURITIES AND EXCHANGE COMMISSION
                            WASHINGTON, D. C. 20549

                               ------------------

                                  FORM 10-K/A

                      AMENDMENT TO FORM 10-K ANNUAL REPORT

                    Filed pursuant to Section 13 or 15(d) of

                      The Securities Exchange Act of 1934

                               ------------------

                               MERCK & CO., INC.

                                  P.O. BOX 100

                   WHITEHOUSE STATION, NEW JERSEY 08889-0100

- --------------------------------------------------------------------------------
- --------------------------------------------------------------------------------
<PAGE>   2

                                AMENDMENT NO. 1

     The undersigned registrant hereby amends the following items, financial
statements, exhibits or other portions of its annual report on Form 10-K for the
fiscal year ended December 31, 1998 as set forth below:

1.  Add Exhibit Numbers 99(a), 99(b) and 99(c) as follows:

<TABLE>
<CAPTION>
EXHIBIT                                                             METHOD OF
NUMBER                  DESCRIPTION                                  FILING
<C>       <S>                                        <C>

99(a)     -- Financial statements and exhibits       Filed with this Form 10-K/A Amendment
             required by Form 11-K Annual Report
             pursuant to Section 15(d) of the
             Securities Exchange Act of 1934 for
             the Merck & Co., Inc. Employee
             Savings and Security Plan for the
             fiscal year ended December 31, 1998

99(b)     -- Financial statements and exhibits       Filed with this Form 10-K/A Amendment
             required by Form 11-K Annual Report
             pursuant to Section 15(d) of the
             Securities Exchange Act of 1934 for
             the Merck & Co., Inc. Employee Stock
             Purchase and Savings Plan for the
             fiscal year ended December 31, 1998

99(c)     -- Financial statements and exhibits       Filed with this Form 10-K/A Amendment
             required by Form 11-K Annual Report
             pursuant to Section 15(d) of the
             Securities Exchange Act of 1934 for
             the Merck Puerto Rico Employee
             Savings and Security Plan for the
             fiscal year ended December 31, 1998
</TABLE>

                                        2
<PAGE>   3

                                   SIGNATURES

     PURSUANT TO THE REQUIREMENTS OF SECTION 13 OR 15(D) OF THE SECURITIES
EXCHANGE ACT OF 1934, THE REGISTRANT HAS DULY CAUSED THIS AMENDMENT TO BE SIGNED
ON ITS BEHALF BY THE UNDERSIGNED, THEREUNTO DULY AUTHORIZED.

                                          MERCK & CO., INC.
Dated:  June 10, 1999
                                               By  RAYMOND V. GILMARTIN
                                          (CHAIRMAN OF THE BOARD, PRESIDENT
                                            AND CHIEF EXECUTIVE OFFICER)

                                                    By  /s/CELIA A. COLBERT
                                                           CELIA A. COLBERT
                                                          (ATTORNEY-IN-FACT)

     PURSUANT TO THE REQUIREMENTS OF THE SECURITIES EXCHANGE ACT OF 1934, THIS
AMENDMENT HAS BEEN SIGNED BELOW BY THE FOLLOWING PERSONS ON BEHALF OF THE
REGISTRANT AND IN THE CAPACITIES AND ON THE DATES INDICATED.

<TABLE>
<CAPTION>
                    SIGNATURES                                       TITLE                        DATE
                    ----------                                       -----                        ----
<C>                                                    <S>                                   <C>

               RAYMOND V. GILMARTIN                    Chairman of the Board,
                                                         President and Chief
                                                         Executive Officer;
                                                         Principal Executive
                                                         Officer; Director

                  JUDY C. LEWENT                       Senior Vice President
                                                         and Chief Financial
                                                         Officer; Principal
                                                         Financial Officer

             RICHARD C. HENRIQUES, JR.                 Vice President, Controller;           June 10, 1999
                                                         Principal Accounting
                                                         Officer
             H. BREWSTER ATWATER, JR.
                   DEREK BIRKIN
                LAWRENCE A. BOSSIDY
                 WILLIAM G. BOWEN                      Directors
                 JOHNNETTA B. COLE
                 CAROLYNE K. DAVIS

                   LLOYD C. ELAM
               CHARLES E. EXLEY, JR.
                 WILLIAM N. KELLEY
                EDWARD M. SCOLNICK
                  SAMUEL O. THIER
                DENNIS WEATHERSTONE
</TABLE>

     CELIA A. COLBERT, BY SIGNING HER NAME HERETO, DOES HEREBY SIGN THIS
DOCUMENT PURSUANT TO POWERS OF ATTORNEY DULY EXECUTED BY THE PERSONS NAMED,
FILED WITH THE SECURITIES AND EXCHANGE COMMISSION AS AN EXHIBIT TO FORM 10-K, ON
BEHALF OF SUCH PERSONS, ALL IN THE CAPACITIES AND ON THE DATE STATED, SUCH
PERSONS INCLUDING A MAJORITY OF THE DIRECTORS OF THE COMPANY.

                                                    By  /s/CELIA A. COLBERT
                                                           CELIA A. COLBERT
                                                          (ATTORNEY-IN-FACT)

                                        3

<PAGE>   1

                                                                   EXHIBIT 99(A)

                       FINANCIAL STATEMENTS AND EXHIBITS
                      REQUIRED BY FORM 11-K ANNUAL REPORT
        PURSUANT TO SECTION 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934

                           COMMISSION FILE NO. 1-3305

                             ---------------------

              MERCK & CO., INC. EMPLOYEE SAVINGS AND SECURITY PLAN
                            (FULL TITLE OF THE PLAN)

                               MERCK & CO., INC.
                                  P.O. BOX 100
                   WHITEHOUSE STATION, NEW JERSEY 08889-0100
             (NAME OF ISSUER OF THE SECURITIES HELD PURSUANT TO THE
            PLAN AND THE ADDRESS OF ITS PRINCIPAL EXECUTIVE OFFICE)
<PAGE>   2

                    REPORT OF INDEPENDENT PUBLIC ACCOUNTANTS

To Merck & Co., Inc.:

     We have audited the accompanying statements of net assets available for
benefits of the Merck & Co., Inc. Employee Savings and Security Plan (the
"Plan") as of December 31, 1998 and 1997, and the related statement of changes
in net assets available for benefits for the year ended December 31, 1998. These
financial statements and the schedules referred to below are the responsibility
of the Plan's management. Our responsibility is to express an opinion on these
financial statements and schedules based on our audits.

     We conducted our audits in accordance with generally accepted auditing
standards. Those standards require that we plan and perform the audit to obtain
reasonable assurance about whether the financial statements are free of material
misstatement. An audit includes examining, on a test basis, evidence supporting
the amounts and disclosures in the financial statements. An audit also includes
assessing the accounting principles used and significant estimates made by
management, as well as evaluating the overall financial statement presentation.
We believe that our audits provide a reasonable basis for our opinion.

     In our opinion, the financial statements referred to above present fairly,
in all material respects, the net assets available for benefits of the Plan as
of December 31, 1998 and 1997, and the changes in its net assets available for
benefits for the year ended December 31, 1998, in conformity with generally
accepted accounting principles.

     Our audits were performed for the purpose of forming an opinion on the
basic financial statements taken as a whole. The supplemental schedules of
assets held for investment purposes and reportable transactions are presented
for purposes of additional analysis and are not a required part of the basic
financial statements but are supplementary information required by the
Department of Labor's Rules and Regulations for Reporting and Disclosure under
the Employee Retirement Income Security Act of 1974. The fund information in the
statements of net assets available for benefits and the statement of changes in
net assets available for benefits is presented for purposes of additional
analysis rather than to present the net assets available for plan benefits and
changes in net assets available for plan benefits of each fund. The supplemental
schedules and fund information have been subjected to the auditing procedures
applied in the audits of the basic financial statements and, in our opinion, are
fairly stated in all material respects in relation to the basic financial
statements taken as a whole.

                                                  ARTHUR ANDERSEN LLP

New York, New York
May 7, 1999

                                        1
<PAGE>   3

                               MERCK & CO., INC.

                       EMPLOYEE SAVINGS AND SECURITY PLAN

                 STATEMENT OF NET ASSETS AVAILABLE FOR BENEFITS

<TABLE>
<CAPTION>
                                                                       MERCK COMMON STOCK FUND
                                                                  ---------------------------------
                                                                  (NON-PARTICIPANT    (PARTICIPANT    T. ROWE PRICE    FIDELITY
                                                                   DIRECTED; SEE     DIRECTED; SEE      BLUE CHIP       EQUITY-
                                                     TOTAL            NOTE 1)           NOTE 1)        GROWTH FUND    INCOME FUND
                                                     -----        ----------------   -------------    -------------   -----------
DECEMBER 31, 1998
- -----------------------------------------------                                                       -----------------------
<S>                                              <C>              <C>                <C>              <C>             <C>
Assets:
  Investments at market value..................  $2,808,322,824     $381,511,822     $1,431,648,885   $258,360,153    $47,329,139
                                                 --------------     ------------     --------------   ------------    -----------
  Receivables
    Employer's contribution....................       3,461,459        1,649,385            673,600        236,072         60,576
    Participants' contributions................       7,883,239               --          4,716,802        851,204        155,933
    Accrued interest and dividends.............       6,753,854        1,371,484          5,200,090             --             --
                                                 --------------     ------------     --------------   ------------    -----------
      Total receivables........................      18,098,552        3,020,869         10,590,492      1,087,276        216,509
                                                 --------------     ------------     --------------   ------------    -----------
Net assets available for benefits..............  $2,826,421,376     $384,532,691     $1,442,239,377   $259,447,429    $47,545,648
                                                 ==============     ============     ==============   ============    ===========
</TABLE>

  The accompanying notes to financial statements are an integral part of this
                              financial statement.

                                        2
<PAGE>   4

<TABLE>
<CAPTION>
                                                                   FIDELITY                     T. ROWE PRICE
                                                    VANGUARD       GROWTH &     T. ROWE PRICE      MID-CAP      EUROPACIFIC
                                                   U.S. GROWTH      INCOME       NEW INCOME        GROWTH         GROWTH
                                                    PORTFOLIO     PORTFOLIO         FUND            FUND           FUND
                                                   -----------    ---------     -------------   -------------   ---------
                                                                            (PARTICIPANT DIRECTED; SEE NOTE 1)
                                                   --------------------------------------------------------------------------
DECEMBER 31, 1998
- -----------------------------------------------
<S>                                                <S>           <C>            <C>             <C>             <C>
Assets:
  Investments at market value..................    $99,320,583   $131,666,327    $35,018,892     $49,950,611    $36,734,926
                                                    ----------    -----------    -----------     -----------     ----------
  Receivables
    Employer's contribution....................        132,228        165,112         39,807          78,921         62,306
    Participants' contributions................        327,226        433,793        115,375         164,569        121,028
    Accrued interest and dividends.............             --             --             --              --             --
                                                    ----------    -----------    -----------     -----------     ----------
      Total receivables........................        459,454        598,905        155,182         243,490        183,334
                                                    ----------    -----------    -----------     -----------     ----------
Net assets available for benefits..............    $99,780,037   $132,265,232    $35,174,074     $50,194,101    $36,918,260
                                                    ==========    ============   ===========     ===========     ==========
</TABLE>



<TABLE>
<CAPTION>
                                                    THE GEORGE      FIDELITY       SPARTAN      FIDELITY
                                                      PUTNAM       RETIREMENT    U.S. EQUITY   LOW-PRICED
                                                      FUND OF        MONEY          INDEX         STOCK
                                                     BOSTON A        MARKET         FUND          FUND
                                                     ----------     ----------   -----------   -----------
                                                               (PARTICIPANT DIRECTED; SEE NOTE 1)
                                                      -----------------------------------------------------
DECEMBER 31, 1998
- -----------------------------------------------
<S>                                                 <C>           <C>            <C>           <C>
Assets:
  Investments at market value..................     $63,465,586   $117,289,314   $65,100,203   $12,095,805
                                                     ----------    -----------    ----------    ----------
  Receivables
    Employer's contribution....................          59,537         85,152        93,113        28,038
    Participants' contributions................         209,096        386,426       214,482        39,851
    Accrued interest and dividends.............              --             --            --            --
                                                     ----------    -----------    ----------    ----------
      Total receivables........................         268,633        471,578       307,595        67,889
                                                     ----------    -----------    ----------    ----------
Net assets available for benefits..............     $63,734,219   $117,760,892   $65,407,798   $12,163,694
                                                     ==========    ===========    ==========    ==========
</TABLE>


                                       3
<PAGE>   5

<TABLE>
<CAPTION>
                                                                            TEMPLETON
                                                FRANKLIN        PUTNAM      DEVELOPING   T. ROWE PRICE   PARTICIPANTS'
                                                SMALL CAP       VOYAGER      MARKETS       DIVIDEND          LOAN
                                              GROWTH FUND I     FUND A       TRUST I      GROWTH FUND       ACCOUNT
                                              -------------     -------     ----------   -------------   -------------
                                               -----------------------------------------------------------------------
DECEMBER 31, 1998
- -----------------------------------------------
<S>                                             <C>           <C>          <C>             <C>             <C>
Assets:
  Investments at market value.................. $15,016,062    $12,728,332   $5,373,422    $11,637,914     $34,074,848
                                                -----------     ----------    ---------    -----------     -----------
  Receivables
    Employer's contribution....................      33,922         29,076       15,230         19,384              --
    Participants' contributions................      49,473         41,935       17,703         38,343              --
    Accrued interest and dividends.............          --             --           --             --         182,280
                                                -----------     ----------    ---------    -----------     -----------
      Total receivables........................      83,395         71,011       32,933         57,727         182,280
                                                -----------     ----------    ---------    -----------     -----------
Net assets available for benefits.............. $15,099,457    $12,799,343   $5,406,355    $11,695,641     $34,257,128
                                                ===========     ==========    =========    ===========     ===========

</TABLE>

                                        4
<PAGE>   6

                               MERCK & CO., INC.

                       EMPLOYEE SAVINGS AND SECURITY PLAN

                 STATEMENT OF NET ASSETS AVAILABLE FOR BENEFITS
<TABLE>
<CAPTION>
                                                           MERCK COMMON STOCK FUND
                                                      ----------------------------------
                                                      (NON-PARTICIPANT     (PARTICIPANT     T. ROWE PRICE     FIDELITY
                                                       DIRECTED; SEE      DIRECTED; SEE       BLUE CHIP       MAGELLAN
                                         TOTAL            NOTE 1)            NOTE 1)         GROWTH FUND        FUND
                                         -----        ----------------    -------------     -------------     --------
DECEMBER 31, 1997
- -----------------------------------                                                         ----------------------------
<S>                                  <C>              <C>                 <C>               <C>             <C>
Assets:
  Investments at market value......  $2,134,239,587     $272,483,529      $1,104,221,533    $198,764,539    $         --
                                     --------------     ------------      --------------    ------------    ------------
  Receivables
    Employer's contribution........       3,137,907        1,493,644             624,444         229,381              --
    Participants' contributions....       7,083,498               --           4,281,527         770,693              --
    Accrued interest and
      dividends....................       6,147,371        1,168,119           4,787,193              --              --
                                     --------------     ------------      --------------    ------------    ------------
      Total receivables............      16,368,776        2,661,763           9,693,164       1,000,074              --
                                     --------------     ------------      --------------    ------------    ------------
Net assets available for
  benefits.........................  $2,150,608,363     $275,145,292      $1,113,914,697    $199,764,613    $         --
                                     ==============     ============      ==============    ============    ============

<CAPTION>

                                      FIDELITY      VANGUARD
                                       EQUITY-     U.S. GROWTH
                                     INCOME FUND    PORTFOLIO
                                     -----------   -----------
- -----------------------------------
<S>                                  <C>           <C>
Assets:
  Investments at market value......  $44,321,055   $58,316,674
                                     -----------   -----------
  Receivables
    Employer's contribution........       61,817       105,747
    Participants' contributions....      171,851       226,118
    Accrued interest and
      dividends....................           --            --
                                     -----------   -----------
      Total receivables............      233,668       331,865
                                     -----------   -----------
Net assets available for
  benefits.........................  $44,554,723   $58,648,539
                                     ===========   ===========
</TABLE>

  The accompanying notes to financial statements are an integral part of this
                              financial statement.

                                        5
<PAGE>   7
<TABLE>
<CAPTION>
                                                                                                                   T. ROWE
                                     FIDELITY       FIDELITY                                        FIDELITY         PRICE
                                      GROWTH        GROWTH &      T. ROWE PRICE      FIDELITY      RETIREMENT       MID-CAP
                                      COMPANY        INCOME        NEW INCOME      INTERMEDIATE      GROWTH         GROWTH
                                       FUND         PORTFOLIO         FUND          BOND FUND         FUND           FUND
                                     --------       ---------     -------------    ------------    ----------       -------
                                                                    (PARTICIPANT DIRECTED; SEE NOTE 1)
                                     -----------------------------------------------------------------------------------------

DECEMBER 31, 1997
- -----------------------------------
<S>                                  <C>            <C>              <C>             <C>            <C>            <C>
Assets:
  Investments at market value......  $        --    $98,415,031     $24,839,606     $        --     $        --    $38,576,112
                                      ----------     ----------     -----------     -----------      ----------     ----------
  Receivables
    Employer's contribution........           --        156,268          33,889              --              --         74,682
    Participants' contributions....           --        381,596          96,313              --              --        149,576
    Accrued interest and
      dividends....................           --             --              --              --              --             --
                                      ----------     ----------     -----------     -----------      ----------     ----------
      Total receivables............           --        537,864         130,202              --              --        224,258
                                      ----------     ----------     -----------     -----------      ----------     ----------
Net assets available for             $        --    $98,952,895     $24,969,808     $        --     $        --    $38,800,370
  benefits.........................   ==========     ==========     ===========     ===========      ==========     ==========
<CAPTION>
                                         FIDELITY                   THE GEORGE
                                       FIDELITY      EUROPACIFIC    GROWTH      FIDELITY        PUTNAM
                                          OTC          GROWTH       COMPANY     OVERSEAS        FUND OF
                                       PORTFOLIO        FUND         FUND         FUND         BOSTON A
                                       ---------     -----------    --------     --------      ----------
                                                         (PARTICIPANT DIRECTED; SEE NOTE 1)
                                     --------------------------------------------------------------------

- -----------------------------------
<S>                                  <C>            <C>          <C>          <C>            <C>
Assets:
  Investments at market value......  $        --    $31,038,262  $        --  $        --    $58,439,910
                                      ----------     ----------   ----------   ----------     ----------
  Receivables
    Employer's contribution........           --         65,502           --           --         58,051
    Participants' contributions....           --        120,248           --           --        226,596
    Accrued interest and
      dividends....................           --             --           --           --             --
                                      ----------     ----------   ----------   ----------     ----------

      Total receivables............           --        183.930           --       26.801        192.059
                                      ----------     ----------   ----------   ----------     ----------
Net assets available for
  benefits.........................  $        --    $31,224,192  $        --  $        --    $58,724,557
                                      ==========    ===========   ==========   ==========     ==========
</TABLE>

                                        6
<PAGE>   8
<TABLE>
<CAPTION>
                                                     FIDELITY        FIDELITY        SPARTAN       FIDELITY
                                      FIDELITY      RETIREMENT      RETIREMENT     U.S. EQUITY    LOW-PRICED       FRANKLIN
                                      BALANCED         MONEY        GOVERNMENT        INDEX          STOCK         SMALL CAP
                                        FUND          MARKET       MONEY MARKET       FUND           FUND        GROWTH FUND I
                                      --------      ----------     ------------    -----------    ----------     -------------
                                     ------------------------------------------------------------------------------------------

DECEMBER 31, 1997
- -----------------------------------
<S>                                  <C>            <C>            <C>             <C>            <C>            <C>
Assets:
  Investments at market value......  $        --    $86,580,252    $        --     $44,776,486    $11,112,462     $12,159,638
                                      ----------     ----------    -----------      ----------     ----------     -----------
  Receivables
    Employer's contribution........           --         75,937             --          75,937         20,083          23,848
    Participants' contributions....           --        335,708             --         173,617         43,088          47,148
    Accrued interest and
      dividends....................           --             --             --              --             --              --
                                      ----------     ----------    -----------      ----------     ----------     -----------
      Total receivables............           --        411,645             --         249,554         63,171          70,996
                                      ----------     ----------    -----------      ----------     ----------     -----------
Net assets available for
  benefits.........................  $        --    $86,991,897    $        --     $45,026,040    $11,175,633     $12,230,634
                                      ==========     ==========    ===========      ==========     ==========     ===========

<CAPTION>


                                                         TEMPLETON
                                           PUTNAM       DEVELOPING     FIDELITY    T. ROWE PRICE    PARTICIPANTS'
                                           VOYAGER        MARKETS      BALANCED      DIVIDEND           LOAN
                                           FUND A         TRUST I        FUND       GROWTH FUND        ACCOUNT
                                           -------      ----------     --------    -------------    -------------
- -----------------------------------
<S>                                        <C>            <C>          <C>          <C>              <C>
Assets:
 Investments at market value......         $ 5,696,444    $ 4,713,493          --   $ 4,888,735      $34,895,826
                                            ----------     ----------  ----------   -----------      -----------
  Receivables
    Employer's contribution........             15,690         15,062          --         7,845               --
    Participants' contributions....             22,087         18,276          --        18,956               --
    Accrued interest and
      dividends....................                 --                         --            --          192,059
                                            ----------     ----------  ----------   -----------      -----------
      Total receivables............             37,777         33,338          --        26,801          192,059
                                            ----------     ----------  ----------   -----------      -----------
Net assets available for
  benefits.........................        $ 5,734,221    $ 4,746,831          --   $ 4,915,536      $35,087,885
                                            ==========     ===========  ==========   ===========      ===========
</TABLE>

                                         7

<PAGE>   9

                               MERCK & CO., INC.

                       EMPLOYEE SAVINGS AND SECURITY PLAN

           STATEMENT OF CHANGES IN NET ASSETS AVAILABLE FOR BENEFITS

<TABLE>
<CAPTION>
                                                          MERCK COMMON STOCK FUND
                                                          -----------------------
                                                           (NON-
                                                        PARTICIPANT     (PARTICIPANT    T. ROWE PRICE    FIDELITY      VANGUARD
                                                       DIRECTED; SEE   DIRECTED; SEE      BLUE CHIP       EQUITY-     U.S. GROWTH
                                          TOTAL           NOTE 1)         NOTE 1)        GROWTH FUND    INCOME FUND    PORTFOLIO
                                      --------------   -------------   -------------    -------------   -----------   -----------
YEAR ENDED DECEMBER 31, 1998
- ------------------------------------                                                    -----------------------------------
<S>                                   <C>              <C>             <C>              <C>             <C>           <C>
Additions to net assets attributed
  to:
  Investment income
    Net appreciation (depreciation)
      in
      market value of investments...  $  631,799,708   $106,270,630    $  408,504,841   $ 52,772,980    $ 2,530,053   $19,189,340
    Interest........................       3,016,847         79,023         1,545,728        382,928         69,568       130,557
    Dividends.......................      64,621,385      5,998,910        18,308,196      4,153,247      2,697,677     6,146,982
                                      --------------   ------------    --------------   ------------    -----------   -----------
      Total investment income
        (loss)......................     699,437,940    112,348,563       428,358,765     57,309,155      5,297,298    25,466,879
                                      --------------   ------------    --------------   ------------    -----------   -----------
  Contributions to the Plan
    By participants.................     115,124,066             --        43,884,054     13,946,071      4,001,088     8,114,697
    By the employer.................      43,546,282     20,646,232         8,499,733      3,060,773        814,150     1,564,420
                                      --------------   ------------    --------------   ------------    -----------   -----------
      Total contributions...........     158,670,348     20,646,232        52,383,787     17,006,844      4,815,238     9,679,117
                                      --------------   ------------    --------------   ------------    -----------   -----------
      Total additions...............     858,108,288    132,994,795       480,742,552     74,315,999     10,112,536    35,145,996
                                      --------------   ------------    --------------   ------------    -----------   -----------
Deductions from net assets
  attributed to:
  Benefits paid to participants.....    (115,762,425)   (14,832,225)      (53,258,583)    (7,482,088)    (1,856,020)   (2,567,789)
                                      --------------   ------------    --------------   ------------    -----------   -----------
Transfers among funds and Plans:
  Net reallocations.................     (66,532,850)    (8,613,566)      (97,734,901)    (7,212,339)    (5,235,198)    8,648,714
  Loans to participants.............              --       (224,743)       (7,781,191)    (1,497,250)      (311,442)     (647,922)
  Loan repayments by participants...              --         63,138         6,356,803      1,558,494        281,049       552,499
                                      --------------   ------------    --------------   ------------    -----------   -----------
      Net transfers among funds and
        Plans.......................     (66,532,850)    (8,775,171)      (99,159,289)    (7,151,095)    (5,265,591)    8,553,291
                                      --------------   ------------    --------------   ------------    -----------   -----------
      Total deductions and net
        transfers
        among funds and Plans.......    (182,295,275)   (23,607,396)     (152,417,872)   (14,633,183)    (7,121,611)    5,985,502
                                      --------------   ------------    --------------   ------------    -----------   -----------
        Net increase (decrease).....     675,813,013    109,387,399       328,324,680     59,682,816      2,990,925    41,131,498
Net assets available for benefits
        Beginning of year...........   2,150,608,363    275,145,292     1,113,914,697    199,764,613     44,554,723    58,648,539
                                      --------------   ------------    --------------   ------------    -----------   -----------
        End of year.................  $2,826,421,376   $384,532,691    $1,442,239,377   $259,447,429    $47,545,648   $99,780,037
                                      ==============   ============    ==============   ============    ===========   ===========
</TABLE>

  The accompanying notes to financial statements are an integral part of this
                              financial statement.

                                        8
<PAGE>   10

<TABLE>
<CAPTION>
                                      FIDELITY                                                              FIDELITY
                                      GROWTH &   T. ROWE PRICE  T. ROWE PRICE                THE GEORGE    RETIREMENT   SPARTAN U.S.
                                       INCOME     NEW INCOME       MID-CAP     EUROPACIFIC  PUTNAM FUND      MONEY      EQUITY INDEX
                                     PORTFOLIO       FUND        GROWTH FUND   GROWTH FUND  OF BOSTON A      MARKET         FUND
                                     ---------   -------------  -------------  -----------  -----------    ----------   ------------
YEAR ENDED DECEMBER 31, 1998          (PARTICIPANT DIRECTED; SEE NOTE 1)
- ------------------------------------------------------------------------------------------------------------------------------------
<S>                                <C>            <C>            <C>          <C>          <C>           <C>           <C>
Additions to net assets
  attributed to:
  Investment income
    Net appreciation
      (depreciation) in
      market value of
      investments................   $ 21,198,292   $  (995,420)   $ 7,482,070  $ 2,668,708  $    193,858  $         --  $12,251,037
    Interest.....................        191,951        42,290         83,747       76,989       106,066       131,579       89,423
    Dividends....................      6,899,853     2,346,887      1,041,930    1,974,488     5,885,452     5,288,736    1,158,513
                                    ------------   -----------    -----------  -----------  ------------  ------------  -----------
      Total investment income
        (loss)...................     28,290,096     1,393,757      8,607,747    4,720,185     6,185,376     5,420,315   13,498,973
                                    ------------   -----------    -----------  -----------  ------------  ------------  -----------
  Contributions to the Plan
    By participants..............     10,308,118     2,481,714      4,949,702    4,080,173     3,545,168     5,236,280    5,954,830
    By the employer..............      2,136,285       480,900      1,010,937      831,454       780,827     1,037,547    1,139,885
                                    ------------   -----------    -----------  -----------  ------------  ------------  -----------
      Total contributions........     12,444,403     2,962,614      5,960,639    4,911,627     4,325,995     6,273,827    7,094,715
                                    ------------   -----------    -----------  -----------  ------------  ------------  -----------
      Total additions............     40,734,499     4,356,371     14,568,386    9,631,812    10,511,371    11,694,142   20,593,688
                                    ------------   -----------    -----------  -----------  ------------  ------------  -----------
Deductions from net assets
  attributed to:
  Benefits paid to participants..     (4,908,589)   (1,197,574)    (1,747,577)    (966,416)   (2,018,908)  (19,189,103)  (2,905,213)
                                    ------------   -----------    -----------  -----------  ------------  ------------  -----------
Transfers among funds and Plans:
  Net reallocations..............     (2,542,045)    7,007,602     (1,486,641)  (3,044,440)   (3,543,399)   38,718,344    2,632,320
  Loans to participants..........       (733,892)     (140,418)      (322,754)    (301,010)     (350,914)   (1,078,285)    (338,237)
  Loan repayments by
    participants.................        762,364       178,285        382,317      374,122       411,512       623,897      399,200
                                    ------------   -----------    -----------  -----------  ------------  ------------  -----------
      Net transfers among funds
        and Plans................     (2,513,573)    7,045,469     (1,427,078)  (2,971,328)   (3,482,801)   38,263,956    2,693,283
                                    ------------   -----------    -----------  -----------  ------------  ------------  -----------
      Total deductions and net
        transfers among funds
        and Plans................     (7,422,162)    5,847,895     (3,174,655)  (3,937,744)   (5,501,709)   19,074,853     (211,930)
                                    ------------   -----------    -----------  -----------  ------------  ------------  -----------
        Net increase (decrease)..     33,312,337    10,204,266     11,393,731    5,694,068     5,009,662    30,768,995   20,381,758

Net assets available for benefits
        Beginning of year........     98,952,895    24,969,808     38,800,370   31,224,192    58,724,557    86,991,897   45,026,040
                                    ------------   -----------    -----------  -----------  ------------  ------------  -----------
        End of year..............   $132,265,232   $35,174,074    $50,194,101  $36,918,260  $ 63,734,219  $117,760,892  $65,407,798
                                    ============   ===========    ===========  ===========  ============  ============  ===========
</TABLE>

                                       9
<PAGE>   11

<TABLE>
<CAPTION>
                                                                                          TEMPLETON
                                              FIDELITY       FRANKLIN        PUTNAM      DEVELOPING    T. ROWE PRICE
                                             LOW-PRICED      SMALL CAP       VOYAGER       MARKETS       DIVIDEND      PARTICIPANTS'
                                             STOCK FUND    GROWTH FUND I     FUND A        TRUST I      GROWTH FUND    LOAN ACCOUNT
                                             ----------    -------------     -------     ----------    -------------   -------------
YEAR ENDED DECEMBER 31, 1998
- ---------------------------------            ---------------------------------------------------------------------------------------
<S>                                         <C>           <C>             <C>          <C>            <C>             <C>
Additions to net assets
  attributed to:
  Investment income
    Net appreciation
      (depreciation) in
      market value of
      investments................            $(1,107,929)   $   (35,688)   $ 1,275,638   $(1,159,030)   $   760,328     $        --
    Interest.....................                 19,808         24,245         15,955        15,587         11,403              --
    Dividends....................              1,044,904        212,877        844,369       110,673        507,691              --
                                             -----------    -----------    -----------   -----------    -----------     -----------
      Total investment income
        (loss)...................                (43,217)       201,434      2,135,962    (1,032,770)     1,279,422              --
                                             -----------    -----------    -----------   -----------    -----------     -----------
  Contributions to the Plan
    By participants..............              1,979,735      2,346,667      1,925,634     1,084,568      1,285,567              --
    By the employer..............                352,930        430,889        328,447       206,254        224,619              --
                                             -----------    -----------    -----------   -----------    -----------     -----------
      Total contributions........              2,332,665      2,777,556      2,254,081     1,290,822      1,510,186              --
                                             -----------    -----------    -----------   -----------    -----------     -----------
      Total additions............              2,289,448      2,978,990      4,390,043       258,052      2,789,608              --
                                             -----------    -----------    -----------   -----------    -----------     -----------
Deductions from net assets
  attributed to:
  Benefits paid to participants..               (863,908)      (342,473)      (171,283)      (88,732)      (282,230)     (1,083,714)
                                             -----------    -----------    -----------   -----------    -----------     -----------
Transfers among funds and Plans:
  Net reallocations..............               (515,675)       156,714      2,837,066       437,984      4,234,546      (1,277,936)
  Loans to participants..........                (81,121)       (64,609)       (76,991)      (27,249)       (31,772)     14,009,800
  Loan repayments by
    participants.................                159,317        140,201         86,287        79,469         69,953     (12,478,907)
                                             -----------    -----------    -----------   -----------    -----------     -----------
      Net transfers among funds
        and Plans................               (437,479)       232,306      2,846,362       490,204      4,272,727         252,957
                                             -----------    -----------    -----------   -----------    -----------     -----------
      Total deductions and net
        transfers among funds
        and Plans................             (1,301,387)      (110,167)     2,675,079       401,472      3,990,497        (830,757)
                                             -----------    -----------    -----------   -----------    -----------     -----------
        Net increase (decrease)..                988,061      2,868,823      7,065,122       659,524      6,780,105        (830,757)

Net assets available for benefits
        Beginning of year........             11,175,633     12,230,634      5,734,221     4,746,831      4,915,536      35,087,885
                                             -----------    -----------    -----------   -----------    -----------     -----------
        End of year..............            $12,163,694    $15,099,457    $12,799,343   $ 5,406,355    $11,695,641     $34,257,128
                                             ===========    ===========    ===========   ===========    ===========     ===========
</TABLE>

                                       10
<PAGE>   12

                               MERCK & CO., INC.

                       EMPLOYEE SAVINGS AND SECURITY PLAN

                         NOTES TO FINANCIAL STATEMENTS

 1. DESCRIPTION OF THE PLAN:

     The Merck & Co., Inc. Employee Savings and Security Plan (the "Plan") was
designed to provide an easy, economical way for employees to become stockholders
of Merck & Co., Inc. (the "Company" or "Merck") as well as a systematic means of
saving and investing for the future. Regular full-time, part-time, and temporary
employees of the Company and of certain wholly-owned subsidiaries as defined by
the Plan document who were not covered by a collective bargaining agreement are
eligible to enroll in the Plan as of the first day of the third month following
their date of hire.

     The Plan is administered by a management committee appointed by the Chief
Executive Officer of the Company. All costs of administering the Plan are borne
by the Company.

     Participants should refer to the Summary Plan Description for a complete
description of benefits provided.

     The Plan is subject to the provisions of the Employee Retirement Income
Security Act of 1974 (ERISA).

     CONTRIBUTIONS

     Participants may contribute from 2% up to 15% of their base pay. In
addition, the Company matches 75% of employee contributions up to 6% of base pay
per pay period. Company matching contributions are invested according to the
following age parameters:

     Under age 50 -- 50% of Company matching contributions is invested in the
Merck Common Stock Fund (Non-participant directed) and 50% is invested in the
funds to which the participant is currently contributing (Participant directed).

     Age 50 and above -- Participants have the option to invest all Company
matching contributions in any of the available fund options (Participant
directed).

     INVESTMENT OPTIONS

     Participants direct the investment of their contributions into any
investment option including the Merck Common Stock Fund (Participant directed).
Participants should refer to each investment fund's prospectus for a more
complete description of the risks and strategies associated with each fund.
Participants may change their investment options daily. The following is a brief
description of each option:

     Merck Common Stock Fund

     The Merck Common Stock Fund invests primarily in Merck common stock and a
small portion of money market instruments for liquidity. This liquidity allows
for daily trading in the fund. Ownership is measured in units rather than
shares. An investment in this option allows the participant to become a
stockholder and part owner of the Company. The value of the investment can go up
or down depending on general factors affecting the stock market and specific
factors affecting the Company's business. This is neither a mutual fund nor a
diversified or managed investment option. Investing in a non-diversified single
stock involves more investment risk than investing in a diversified fund.

     T. Rowe Price Blue Chip Growth Fund

     The T. Rowe Price Blue Chip Growth Fund seeks to provide long-term growth
of capital. The fund invests primarily (at least 65% of its assets) in common
stocks of large and medium-sized blue chip companies

                                       11
<PAGE>   13
                               MERCK & CO., INC.

                       EMPLOYEE SAVINGS AND SECURITY PLAN

                  NOTES TO FINANCIAL STATEMENTS -- (CONTINUED)

that have the potential for above-average earnings growth and are well
established in their respective industries. The fund may also invest in
convertible stocks and bonds, preferred stocks, bonds and warrants. Up to 20% of
assets (excluding reserves) may be invested in foreign securities, which may be
subject to currency risks and political and sovereign risks of the home country.

     Fidelity Equity-Income Fund

     Funds are invested in income-producing equity securities. Normally, at
least 65% of the fund's assets will be invested in income producing equity
securities. The fund has the flexibility to invest the balance in all types of
domestic and foreign securities, including bonds.

     Vanguard U.S. Growth Portfolio

     The Vanguard U.S. Growth Portfolio seeks to provide long-term capital
growth by investing in equity securities of large, established U.S. companies
that have good growth records, strong market positions and have exhibited
long-term financial strength to provide potential long-term growth.

     Fidelity Growth & Income Portfolio

     Funds are invested primarily in U.S. and foreign stocks, focusing on those
that pay current dividends and offer potential growth of earnings such as common
stocks, convertible securities, preferred stocks and warrants.

     T. Rowe Price New Income Fund

     The T. Rowe Price New Income Fund is a bond fund that seeks to provide the
highest level of income consistent with preservation of capital by purchasing
securities that have been rated as investment-grade by Standard & Poor's,
Moody's or Fitch Investor Services. The fund invests at least 80% of its assets
in income-producing investment-grade debt securities including U.S. government
and agency securities, corporate bonds, bank obligations and utilities. The
fund's dollar-weighted average maturity is generally expected to be between four
and fifteen years.

     T. Rowe Price Mid-Cap Growth Fund

     The T. Rowe Price Mid-Cap Growth Fund seeks to provide long-term capital
appreciation by investing primarily in the stock of medium-sized (mid-cap)
growth companies that offer the potential for above-average earnings growth. The
fund focuses on companies that are no longer considered new or emerging, but are
well-established. It may also invest in convertible securities, warrants and
foreign securities, which are subject to greater risks.

     EuroPacific Growth Fund

     This fund seeks long-term capital growth by investing primarily in
securities of companies outside the United States. Normally, at least 65% of the
fund's total assets will be invested in Europe or the Pacific Basin. The Pacific
Basin is generally defined as those countries bordering the Pacific Ocean and
includes, but is not limited to Australia, Canada, Japan, Malaysia and
Singapore. The fund may also invest in convertible securities, debt and
government securities and preferred stock. Foreign investments, especially in
developing countries, involve greater risks and may offer greater potential.

                                       12
<PAGE>   14
                               MERCK & CO., INC.

                       EMPLOYEE SAVINGS AND SECURITY PLAN

                  NOTES TO FINANCIAL STATEMENTS -- (CONTINUED)

     The George Putnam Fund of Boston A

     This fund seeks to provide a balanced investment comprised of a
well-diversified portfolio of stocks and bonds that will produce both capital
growth and current income. Normally, no more than 75% of the fund's assets will
be invested in common stocks and convertible securities.

     Fidelity Retirement Money Market

     Funds are invested in high-quality U.S. dollar-denominated money market
instruments of U.S. and foreign issuers. Normally, the fund intends to invest
more than 25% of its total assets in obligations of institutions in the
financial services industry.

     Spartan U.S. Equity Index Fund

     This fund seeks to provide investment results that correspond to the total
return performance of common stocks traded in the United States. Funds are
primarily invested in securities of the companies which comprise the S&P 500
Index.

     Fidelity Low-Priced Stock Fund

     This fund seeks capital appreciation by investing mainly in low-priced
domestic and foreign common stocks ($35 or less at time of purchase). Foreign
securities may involve a higher degree of risk. This fund charges a redemption
fee to discourage short-term buying and selling of fund shares. If fund shares
are sold after being held for less than 90 days, the fund will deduct a
redemption fee from participants' accounts equal to 1.5% of the value of the
shares sold.

     Franklin Small Cap Growth Fund I

     This fund seeks long-term capital growth by investing primarily in stocks
of companies with market capitalization of less than $1.5 billion at the time of
the investment. Although the fund's assets are invested primarily in small
companies, it may invest up to 35% of its total assets in larger capitalized
companies with strong growth potential, in relatively well-known larger
companies in mature industries with potential for capital appreciation, and in
corporate debt securities, including bonds, notes and debentures if deemed
appropriate. The fund may also invest up to 25% of its total assets in foreign
securities, which may involve greater risks.

     Effective January 1, 1999, the Franklin Small Cap Growth Fund I shares were
changed to Class A.

     Putnam Voyager Fund A

     This fund seeks capital appreciation by investing primarily in common
stocks of companies that have potential for capital appreciation which is
significantly greater than that of the market averages. The fund may also invest
in convertible bonds, convertible preferred stocks, warrants, preferred stocks,
money market instruments and debt securities. The fund may invest up to 20% of
its total assets in securities principally traded in foreign markets. Foreign
securities are subject to currency, political, financial or sovereign risks of
the issuer's home country.

     Templeton Developing Markets Trust I

     This fund seeks long-term capitalization by investing in equity securities
of emerging market countries. The fund may invest up to 35% of its total assets
in debt securities, including bonds, notes, debentures,
                                       13
<PAGE>   15
                               MERCK & CO., INC.

                       EMPLOYEE SAVINGS AND SECURITY PLAN

                  NOTES TO FINANCIAL STATEMENTS -- (CONTINUED)

commercial paper, certificates of deposit, time deposits and bankers'
acceptances. Foreign investments may involve greater risks.

     Effective January 1, 1999, the Templeton Developing Markets Trust I shares
were changed to Class A.

     T. Rowe Price Dividend Growth Fund

     This fund seeks to provide increasing dividend income over time, long-term
capital appreciation and reasonable current income through investments primarily
in dividend-paying stocks. The fund may also invest in bonds and foreign
securities.

     VESTING

     Participants are immediately vested in their contributions, all Company
matching contributions, plus actual earnings thereon.

     PLAN TERMINATION

     Although it has not expressed any intent to do so, the Company has the
right under the Plan to discontinue its contributions at any time and to
terminate the Plan subject to the provisions of the Employee Retirement Income
Security Act of 1974.

     PARTICIPANTS' LOAN ACCOUNT

     Participants may borrow from their account balances with interest charged
at the prime rate plus 1%. Loan terms range from one to five years or up to
thirty years for the purchase of a primary residence. The minimum loan is $500
and the maximum loan is the lesser of $50,000 less the highest outstanding loan
balance during the one year period prior to the new loan application date, or
50% of the participant's account balance less any current outstanding loan
balance. Activity related to these borrowings is reflected in the Participants'
Loan Account column of the financial statements.

     BENEFITS PAID TO PARTICIPANTS

     In-service (which include hardship withdrawals) and termination
distributions are made throughout the year in accordance with applicable Plan
provisions. At December 31, 1998 and 1997, net assets available for benefits
included distributions in process of payment of $1,816,514 and $3,134,986,
respectively.

 2. SUMMARY OF ACCOUNTING POLICIES:

     The financial statements of the Plan have been prepared on the accrual
basis of accounting. The investments of the Plan are stated at quoted market
value. Dividend income is recorded on the ex-dividend date. The net appreciation
(depreciation) in market value of investments is based on the beginning of the
year market value or value at the time of purchase during the year and is
included in the statement of changes in net assets available for benefits.

     USE OF ESTIMATES

     The financial statements are prepared in conformity with generally accepted
accounting principles and, accordingly, include amounts that are based on
management's best estimates and judgments. Actual results could differ from
these estimates.

                                       14
<PAGE>   16
                               MERCK & CO., INC.

                       EMPLOYEE SAVINGS AND SECURITY PLAN

                  NOTES TO FINANCIAL STATEMENTS -- (CONTINUED)

 3.  INCOME TAXES:

     The Plan obtained a tax determination letter from the Internal Revenue
Service on September 18, 1995 indicating that it had been designed in accordance
with applicable sections of the Internal Revenue Code ("IRC"). The Plan was most
recently amended in May 1998. The Plan sponsor believes that the Plan is
designed and currently operated in compliance with the IRC. Therefore, no
provision for income taxes has been made.

 4.  OTHER MATTERS:

     Net reallocations and transfers in 1998 of ($66,532,850) consist of (a)
($67,808,073) for employees in Merck's AgVet division and associated operations
who were transferred on January 1, 1998 to Merial Limited, a stand-alone joint
venture that is 50% owned by Merck & Co., Inc. and 50% owned by Rhone-Poulenc
SA, and whose fund accounts were transferred to Merial's savings plan, (b)
$1,272,189 transferred between the Plan and the Merck & Co., Inc. Stock Purchase
and Savings Plan for employees who changed their status during the year, (c)
$622,160 for employees who transferred from Merck-Medco Managed Care, L.L.C.
during the year, (d) ($158,338) transferred from the Plan to the Merck Puerto
Rico Employee Savings and Security Plan for employees who changed their status
during the year and (e) the remaining amount relates to miscellaneous net
transfers.

 5.  PARTY-IN-INTEREST:

     All party-in-interest transactions are set forth on the attached schedules.

 6.  PROHIBITED TRANSACTIONS:

     There were no prohibited transactions during 1998.

                                       15
<PAGE>   17

                                                           SCHEDULE I
                                                           EIN:  22-1109110
                                                           PLAN NO.:  001

                               MERCK & CO., INC.

                       EMPLOYEE SAVINGS AND SECURITY PLAN

          ITEM 27a -- SCHEDULE OF ASSETS HELD FOR INVESTMENT PURPOSES

                               DECEMBER 31, 1998

<TABLE>
<CAPTION>
                                                                NUMBER OF
                                                             UNITS/SHARES AT
             NAME OF ISSUER AND TITLE OF ISSUE               CLOSE OF PERIOD         COST         CURRENT VALUE
             ---------------------------------               ---------------    --------------    -------------
<S>                                                          <C>                <C>               <C>
Merck Common Stock Fund*....................................    71,924,065      $  561,326,840    $1,813,160,707
T. Rowe Price Blue Chip Growth Fund.........................     8,443,142         193,462,888       258,360,153
Fidelity Equity-Income Fund.................................       852,023          38,341,714        47,329,139
Vanguard U.S. Growth Portfolio..............................     2,649,255          80,294,605        99,320,583
Fidelity Growth & Income Portfolio..........................     2,872,334          92,148,917       131,666,327
T. Rowe Price New Income Fund...............................     3,974,903          35,614,416        35,018,892
T. Rowe Price Mid-Cap Growth Fund...........................     1,465,687          40,440,928        49,950,611
EuroPacific Growth Fund.....................................     1,293,483          36,951,335        36,734,926
The George Putnam Fund of Boston A..........................     3,518,048          63,975,373        63,465,586
Fidelity Retirement Money Market............................   117,261,392         117,261,392       117,289,314
Spartan U.S. Equity Index Fund..............................     1,480,900          45,377,760        65,100,203
Fidelity Low-Priced Stock Fund..............................       529,357          12,957,386        12,095,805
Franklin Small Cap Growth Fund I............................       665,311          15,200,710        15,016,062
Putnam Voyager Fund A.......................................       580,672          11,595,372        12,728,332
Templeton Developing Markets Trust I........................       521,691           7,437,819         5,373,422
T. Rowe Price Dividend Growth Fund..........................       528,756          10,867,188        11,637,914
Participants' Loan Account (with interest rates ranging from
  9.0% to 9.5%).............................................      --                34,074,848        34,074,848
                                                                                --------------    --------------
        Total Investments...................................                    $1,397,329,491    $2,808,322,824
                                                                                ==============    ==============
</TABLE>

- ---------------

* Denotes a party-in-interest to the Plan.

                                       16
<PAGE>   18

                                                           SCHEDULE II
                                                           EIN:  22-1109110
                                                           PLAN NO.:  001

                               MERCK & CO., INC.

                       EMPLOYEE SAVINGS AND SECURITY PLAN

               ITEM 27D -- SCHEDULE OF REPORTABLE TRANSACTIONS(A)

                      FOR THE YEAR ENDED DECEMBER 31, 1998

<TABLE>
<CAPTION>
                                                                                                    CURRENT
                                                                                                     VALUE
                                                                                                  OF ASSETS ON
IDENTITY OF PARTY INVOLVED AND DESCRIPTION OF      PURCHASE                         COST OF       TRANSACTION
ASSETS                                              PRICE        SELLING PRICE       ASSET            DATE          NET GAIN
- ---------------------------------------------    ------------    -------------    ------------    ------------    ------------
<S>                                              <C>             <C>              <C>             <C>             <C>
Merck Common Stock Fund*
   253 Purchase Transactions..............       $254,494,278    $         --     $254,494,278    $254,494,278    $         --
   253 Sales Transactions.................                 --     332,804,323      174,829,803     332,804,323     157,974,520
Fidelity Retirement Money Market
   256 Purchase Transactions..............        216,372,786              --      216,372,786     216,372,786              --
   252 Sales Transactions.................                 --     185,663,496      185,663,496     185,663,496              --
</TABLE>

- ---------------
(a) Reportable transactions are transactions that, individually or in the
    aggregate, exceed 5% of the Plan's net assets as of the beginning of the
    Plan year.
  * Denotes a party-in-interest to the Plan.

                                       17
<PAGE>   19

                                                                      EXHIBIT 23

                   CONSENT OF INDEPENDENT PUBLIC ACCOUNTANTS

     As independent public accountants, we hereby consent to the incorporation
by reference of our report dated May 7, 1999 included in the financial
statements and exhibits required by Form 11-K Annual Report for the Merck & Co.,
Inc. Employee Savings and Security Plan into the Company's previously filed
Registration Statements on Form S-8 (Nos. 33-21087, 33-21088, 33-36101,
33-40177, 33-51235, 33-53463, 33-64273, 33-64665, 333-23293 and 333-23295), on
Form S-4 (No. 33-50667) and on Form S-3 (Nos. 33-60322, 33-39349, 33-51785,
33-57421, 333-17045, 333-36383 and 333-77569). It should be noted that we have
not audited any financial statements of the Plan subsequent to December 31, 1998
or performed any audit procedures subsequent to the date of our report.

                                            ARTHUR ANDERSEN LLP

New York, New York
June 10, 1999

<PAGE>   1

                                                                   EXHIBIT 99(B)

                       FINANCIAL STATEMENTS AND EXHIBITS
                      REQUIRED BY FORM 11-K ANNUAL REPORT
        PURSUANT TO SECTION 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934

                           COMMISSION FILE NO. 1-3305

                             ---------------------

           MERCK & CO., INC. EMPLOYEE STOCK PURCHASE AND SAVINGS PLAN
                            (Full title of the plan)

                               MERCK & CO., INC.
                                  P.O. BOX 100
                   WHITEHOUSE STATION, NEW JERSEY 08889-0100
             (Name of issuer of the securities held pursuant to the
            plan and the address of its principal executive office)
<PAGE>   2

                    REPORT OF INDEPENDENT PUBLIC ACCOUNTANTS

To Merck & Co., Inc.:

     We have audited the accompanying statements of net assets available for
benefits of the Merck & Co., Inc. Employee Stock Purchase and Savings Plan (the
"Plan") as of December 31, 1998 and 1997, and the related statement of changes
in net assets available for benefits for the year ended December 31, 1998. These
financial statements and the schedules referred to below are the responsibility
of the Plan's management. Our responsibility is to express an opinion on these
financial statements and schedules based on our audits.

     We conducted our audits in accordance with generally accepted auditing
standards. Those standards require that we plan and perform the audit to obtain
reasonable assurance about whether the financial statements are free of material
misstatement. An audit includes examining, on a test basis, evidence supporting
the amounts and disclosures in the financial statements. An audit also includes
assessing the accounting principles used and significant estimates made by
management, as well as evaluating the overall financial statement presentation.
We believe that our audits provide a reasonable basis for our opinion.

     In our opinion, the financial statements referred to above present fairly,
in all material respects, the net assets available for benefits of the Plan as
of December 31, 1998 and 1997, and the changes in its net assets available for
benefits for the year ended December 31, 1998, in conformity with generally
accepted accounting principles.

     Our audits were performed for the purpose of forming an opinion on the
basic financial statements taken as a whole. The supplemental schedules of
assets held for investment purposes and reportable transactions are presented
for purposes of additional analysis and are not a required part of the basic
financial statements but are supplementary information required by the
Department of Labor's Rules and Regulations for Reporting and Disclosure under
the Employee Retirement Income Security Act of 1974. The fund information in the
statements of net assets available for benefits and the statement of changes in
net assets available for benefits is presented for purposes of additional
analysis rather than to present the net assets available for plan benefits and
changes in net assets available for plan benefits of each fund. The supplemental
schedules and fund information have been subjected to the auditing procedures
applied in the audits of the basic financial statements and, in our opinion, are
fairly stated in all material respects in relation to the basic financial
statements taken as a whole.

                                          ARTHUR ANDERSEN LLP

New York, New York
May 7, 1999

                                        1
<PAGE>   3

                               MERCK & CO., INC.

                    EMPLOYEE STOCK PURCHASE AND SAVINGS PLAN

                 STATEMENT OF NET ASSETS AVAILABLE FOR BENEFITS

<TABLE>
<CAPTION>
                                                                            MERCK COMMON STOCK FUND
                                                                         -----------------------------
                                                                             (NON-                         T. ROWE      FIDELITY
                                                                          PARTICIPANT    (PARTICIPANT       PRICE       EQUITY-
                                                                         DIRECTED; SEE   DIRECTED; SEE    BLUE CHIP      INCOME
                                                             TOTAL          NOTE 1)         NOTE 1)      GROWTH FUND      FUND
                                                             -----       -------------   -------------   -----------    --------
DECEMBER 31, 1998
- --------------------------------------------------------                                                 ---------------------
<S>                                                       <C>            <C>             <C>             <C>           <C>
Assets:
  Investments at market value...........................  $366,805,677    $52,208,941    $254,671,562    $14,973,705   $2,176,087
                                                          ------------    -----------    ------------    -----------   ----------
  Receivables
    Employer's contribution.............................        66,729         35,945          22,381          2,095          360
    Participants' contributions.........................       237,677             --         197,392         11,606        1,687
    Accrued interest and dividends......................     1,102,289        187,665         905,266             --           --
                                                          ------------    -----------    ------------    -----------   ----------
      Total receivables.................................     1,406,695        223,610       1,125,039         13,701        2,047
                                                          ------------    -----------    ------------    -----------   ----------
Net assets available for benefits.......................  $368,212,372    $52,432,551    $255,796,601    $14,987,406   $2,178,134
                                                          ============    ===========    ============    ===========   ==========
</TABLE>

  The accompanying notes to financial statements are an integral part of this
                              financial statement.

                                        2
<PAGE>   4
<TABLE>
<CAPTION>
                                                         FIDELITY                                                      THE GEORGE
                                           VANGUARD       GROWTH &     T. ROWE PRICE    T. ROWE PRICE                     PUTNAM
                                          U.S. GROWTH      INCOME       NEW INCOME         MID-CAP       EUROPACIFIC     FUND OF
                                          PORTFOLIO     PORTFOLIO         FUND          GROWTH FUND     GROWTH FUND     BOSTON A
                                          -----------    ---------     -------------    -------------    -----------    ----------
DECEMBER 31, 1998                                                    (PARTICIPANT DIRECTED; SEE NOTE 1)
- ----------------------------------------------------------------------------------------------------------------------------------
<S>                                       <C>            <C>           <C>              <C>              <C>            <C>
Assets:
  Investments at market value............ $3,771,723     $5,366,261     $1,461,033       $1,827,382      $1,889,995     $5,652,596
                                          ----------     ----------     ----------       ----------      ----------     ----------
  Receivables
    Employer's contribution..............        744            881            287              354             367           834
    Participants' contributions..........      2,923          4,159          1,132            1,416           1,465         4,381
    Accrued interest and dividends.......         --             --             --               --              --            --
                                          ----------     ----------     ----------       ----------      ----------     ----------
      Total receivables..................      3,667          5,040          1,419            1,770           1,832         5,215
                                          ----------     ----------     ----------       ----------      ----------     ----------
Net assets available for benefits........ $3,775,390     $5,371,301     $1,462,452       $1,829,152      $1,891,827     $5,657,811
                                          ==========     ==========     ==========       ==========      ==========     ==========

<CAPTION>
                                                        FIDELITY
                                           VANGUARD    RETIREMENT     SPARTAN U.S.     FIDELITY
                                          U.S. GROWTH     MONEY       EQUITY INDEX    LOW-PRICED
                                           PORTFOLIO     MARKET           FUND        STOCK FUND
                                          -----------  ----------     ------------    ----------
DECEMBER 31, 1998                                         (PARTICIPANT DIRECTED; SEE NOTE 1)
- ------------------------------------------------------------------------------------------------
<S>                                      <C>          <C>            <C>             <C>
Assets:
  Investments at market value........... $3,771,723   $10,010,154     $1,868,618      $436,243
                                         ----------   -----------     ----------      --------
  Receivables
    Employer's contribution.............        744         1,448            334           140
    Participants' contributions.........      2,923         7,759          1,448           338
    Accrued interest and dividends......         --            --             --            --
                                         ----------   -----------     ----------      --------
      Total receivables.................      3,667         9,207          1,782           478
                                         ----------   -----------     ----------      --------
Net assets available for benefits....... $3,775,390   $10,019,361     $1,870,400      $436,721
                                         ==========   ===========     ==========      ========
</TABLE>

                                        3
<PAGE>   5

<TABLE>
<CAPTION>
                                                                                        TEMPLETON
                                                           FRANKLIN         PUTNAM      DEVELOPING    T. ROWE PRICE
                                                           SMALL CAP       VOYAGER       MARKETS        DIVIDEND       PARTICIPANTS'
                                                         GROWTH FUND I      FUND A       TRUST I       GROWTH FUND     LOAN ACCOUNT
                                                         -------------     -------      ----------    -------------    -------------
DECEMBER 31, 1998
- ------------------------------------------------------------------------------------------------------------------------------------
<S>                                                        <C>            <C>            <C>            <C>             <C>
Assets:                                                    $550,170       $1,100,487     $204,899       $687,684        $7,948,137
  Investments at market value...........................   --------       ----------     --------       --------        ----------

  Receivables
    Employer's contribution.............................        173              180           93            113                --
    Participants' contributions.........................        426              853          159            533                --
    Accrued interest and dividends......................         --               --           --             --             9,358
                                                           --------       ----------     --------       --------        ----------
      Total receivables.................................        599            1,033          252            646             9,358
                                                           --------       ----------     --------       --------        ----------
Net assets available for benefits.......................   $550,769       $1,101,520     $205,151       $688,330        $7,957,495
                                                           ========       ==========     ========       ========        ==========
</TABLE>
                                        4
<PAGE>   6

                               MERCK & CO., INC.

                    EMPLOYEE STOCK PURCHASE AND SAVINGS PLAN

                 STATEMENT OF NET ASSETS AVAILABLE FOR BENEFITS

<TABLE>
<CAPTION>
                                                              MERCK COMMON STOCK FUND
                                                           -----------------------------
                                                               (NON-                         T. ROWE                    FIDELITY
                                                            PARTICIPANT    (PARTICIPANT       PRICE       FIDELITY      EQUITY-
                                                           DIRECTED; SEE   DIRECTED; SEE    BLUE CHIP     MAGELLAN       INCOME
                                               TOTAL          NOTE 1)         NOTE 1)      GROWTH FUND      FUND          FUND
                                               -----       -------------   -------------   -----------    --------      --------
DECEMBER 31, 1997
- ------------------------------------------                                                 ---------------------------------
<S>                                         <C>            <C>             <C>             <C>           <C>           <C>
Assets:
  Investments at market value.............  $269,920,909    $49,466,644    $173,227,643    $11,198,335   $        --   $1,895,866
                                            ------------    -----------    ------------    -----------   -----------   ----------
  Receivables
    Employer's contribution...............        77,521         77,521              --             --            --           --
    Participants' contributions...........       360,190             --         292,723         18,923            --        3,204
    Accrued interest and dividends........       962,735        211,323         735,968             --            --           --
                                            ------------    -----------    ------------    -----------   -----------   ----------
      Total receivables...................     1,400,446        288,844       1,028,691         18,923            --        3,204
                                            ------------    -----------    ------------    -----------   -----------   ----------
Net assets available for benefits.........  $271,321,355    $49,755,488    $174,256,334    $11,217,258   $        --   $1,899,070
                                            ============    ===========    ============    ===========   ===========   ==========
</TABLE>

  The accompanying notes to financial statements are an integral part of this
                              financial statement.

                                        5
<PAGE>   7
<TABLE>
<CAPTION>
                                                            FIDELITY     FIDELITY                                       FIDELITY
                                              VANGUARD       GROWTH      GROWTH &     T. ROWE PRICE      FIDELITY      RETIREMENT
                                             U.S. GROWTH    COMPANY       INCOME       NEW INCOME      INTERMEDIATE      GROWTH
                                              PORTFOLIO       FUND      PORTFOLIO         FUND          BOND FUND         FUND
                                             -----------    --------    ---------     -------------    ------------    ----------
DECEMBER 31, 1997                                                     (PARTICIPANT DIRECTED; SEE NOTE 1)
- -----------------------------------------------------------------------------------------------------------------------------------
<S>                                          <C>            <C>          <C>             <C>             <C>             <C>
Assets:
  Investments at market value.............   $2,006,198     $    --      $3,664,353      $966,177         $     --       $     --
                                             ----------     --------     ----------      --------         --------       --------
  Receivables
    Employer's contribution...............           --          --              --            --               --             --
    Participants' contributions...........        3,390          --           6,192         1,633               --             --
    Accrued interest and dividends........           --          --              --            --               --             --
                                             ----------     --------     ----------      --------         --------       --------
      Total receivables...................        3,390          --           6,192         1,633               --             --
                                             ----------     --------     ----------      --------         --------       --------
Net assets available for benefits.........   $2,009,588     $    --      $3,670,545      $967,810         $     --       $     --
                                             ==========     ========     ==========      ========         ========       ========

<CAPTION>
                                             T. ROWE PRICE   VANGUARD      FIDELITY                      FIDELITY
                                                MID-CAP     U.S. GROWTH      OTC        EUROPACIFIC      OVERSEAS
                                              GROWTH FUND    PORTFOLIO    PORTFOLIO     GROWTH FUND        FUND
                                             -------------  -----------   ---------     -----------      --------
DECEMBER 31, 1997                                                (PARTICIPANT DIRECTED; SEE NOTE 1)
- --------------------------------------------------------------------------------------------------------------------
<S>                                          <C>            <C>            <C>          <C>              <C>
Assets:
  Investments at market value.............   $1,591,041     $2,006,198     $     --     $1,349,190       $     --
                                             ----------     ----------     --------     ----------       --------
  Receivables
    Employer's contribution...............           --             --           --             --             --
    Participants' contributions...........        2,689          3,390           --          2,280             --
    Accrued interest and dividends........           --             --           --             --             --
                                             ----------     ----------     --------     ----------       --------
      Total receivables...................        2,689          3,390           --          2,280             --
                                             ----------     ----------     --------     ----------       --------
Net assets available for benefits.........   $1,593,730     $2,009,588     $     --     $1,351,470       $     --
                                             ==========     ==========     ========     ==========       ========
</TABLE>

                                        6
<PAGE>   8

<TABLE>
<CAPTION>
                                             THE GEORGE                 FIDELITY       FIDELITY
                                               PUTNAM      FIDELITY    RETIREMENT     RETIREMENT       SPARTAN       FIDELITY
                                              FUND OF      BALANCED      MONEY        GOVERNMENT     U.S. EQUITY    LOW-PRICED
                                              BOSTON A       FUND        MARKET      MONEY MARKET    INDEX FUND     STOCK FUND
DECEMBER 31, 1997                            ----------    --------    ----------    ------------    -----------    ----------
 -----------------------------------------------------------------------------------------------------------------------------
<S>                                          <C>           <C>         <C>           <C>             <C>            <C>
Assets:
  Investments at market value.............   $4,889,792    $    --     $9,317,599      $     --      $1,076,594      $460,669
                                             ----------    --------    ----------      --------      ----------      --------
  Receivables
    Employer's contribution...............          --          --            --             --              --            --
    Participants' contributions...........       8,263          --        15,745             --           1,819           778
    Accrued interest and dividends........          --          --            --             --              --            --
                                             ----------    --------    ----------      --------      ----------      --------
      Total receivables...................       8,263          --        15,745             --           1,819           778
                                             ----------    --------    ----------      --------      ----------      --------
Net assets available for benefits.........   $4,898,055    $    --     $9,333,344      $     --      $1,078,413      $461,447
                                             ==========    ========    ==========      ========      ==========      ========

<CAPTION>
                                                                          TEMPLETON      THE GEORGE
                                               FRANKLIN        PUTNAM     DEVELOPING       PUTNAM    T. ROWE PRICE
                                               SMALL CAP      VOYAGER      MARKETS        FUND OF      DIVIDEND       PARTICIPANTS'
                                             GROWTH FUND I     FUND A      TRUST I        BOSTON A    GROWTH FUND     LOAN ACCOUNT
DECEMBER 31, 1997                            -------------    -------     ----------     ----------  --------------   -------------
 -----------------------------------------------------------------------------------------------------------------------------------
<S>                                          <C>              <C>           <C>          <S>           <C>            <C>
Assets:
  Investments at market value.............      $492,967      $463,264      $250,691     $4,889,792      $302,591      $7,301,295
                                                --------      --------      --------     ----------      --------      ----------
  Receivables
    Employer's contribution...............            --            --            --             --            --              --
    Participants' contributions...........           833           783           424          8,263           511              --
    Accrued interest and dividends........            --            --            --             --            --          15,444
                                                --------      --------      --------     ----------      --------      ----------
      Total receivables...................           833           783           424          8,263           511          15,444
                                                --------      --------      --------     ----------      --------      ----------
Net assets available for benefits.........      $493,800      $464,047      $251,115     $4,898,055      $303,102      $7,316,739
                                                ========      ========      ========     ==========      ========      ==========
</TABLE>

                                                            7
<PAGE>   9

                               MERCK & CO., INC.

                    EMPLOYEE STOCK PURCHASE AND SAVINGS PLAN

           STATEMENT OF CHANGES IN NET ASSETS AVAILABLE FOR BENEFITS

<TABLE>
<CAPTION>
                                                                         MERCK COMMON STOCK FUND
                                                                      -----------------------------
                                                                          (NON-
                                                                       PARTICIPANT    (PARTICIPANT    T. ROWE PRICE    FIDELITY
                                                                      DIRECTED; SEE   DIRECTED; SEE     BLUE CHIP       EQUITY-
                                                          TOTAL          NOTE 1)         NOTE 1)       GROWTH FUND    INCOME FUND
                                                          -----       -------------   -------------   -------------   -----------
YEAR ENDED DECEMBER 31, 1998
- ---------------------------                                                                           ----------------------
<S>                                                    <C>            <C>             <C>             <C>             <C>
Additions to net assets attributed to:
  Investment income
    Net appreciation (depreciation) in market value
      of investments.................................  $ 90,404,944    $ 7,502,221    $ 77,336,318     $ 3,065,873    $  117,433
    Interest.........................................       680,316         83,269         459,741          43,489         4,545
    Dividends........................................     6,353,557        785,812       3,300,319         239,713       120,389
                                                       ------------    -----------    ------------     -----------    ----------
      Total investment income (loss).................    97,438,817      8,371,302      81,096,378       3,349,075       242,367
                                                       ------------    -----------    ------------     -----------    ----------
  Contributions to the Plan
    By participants..................................    16,195,706             --      10,776,108       1,270,416       252,057
    By the employer..................................     3,308,056      2,030,182         945,031          84,384        14,563
                                                       ------------    -----------    ------------     -----------    ----------
      Total contributions............................    19,503,762      2,030,182      11,721,139       1,354,800       266,620
                                                       ------------    -----------    ------------     -----------    ----------
      Total additions................................   116,942,579     10,401,484      92,817,517       4,703,875       508,987
                                                       ------------    -----------    ------------     -----------    ----------
Deductions from net assets attributed to:
  Benefits paid to participants......................   (18,779,373)    (3,460,117)    (10,504,664)       (545,448)     (109,094)
                                                       ------------    -----------    ------------     -----------    ----------
Transfers among funds and Plans:
  Net reallocations..................................    (1,272,189)    (4,402,680)         29,322        (384,290)     (111,900)
  Loans to participants..............................            --       (222,872)     (2,767,081)       (176,340)      (24,931)
  Loan repayments by participants....................            --        361,248       1,965,173         172,351        16,002
                                                       ------------    -----------    ------------     -----------    ----------
      Net transfers among funds and Plans............    (1,272,189)    (4,264,304)       (772,586)       (388,279)     (120,829)
                                                       ------------    -----------    ------------     -----------    ----------
      Total deductions and net transfers among funds
        and Plans....................................   (20,051,562)    (7,724,421)    (11,277,250)       (933,727)     (229,923)
                                                       ------------    -----------    ------------     -----------    ----------
        Net increase (decrease)......................    96,891,017      2,677,063      81,540,267       3,770,148       279,064
Net assets available for benefits
        Beginning of year............................   271,321,355     49,755,488     174,256,334      11,217,258     1,899,070
                                                       ------------    -----------    ------------     -----------    ----------
        End of year..................................  $368,212,372    $52,432,551    $255,796,601     $14,987,406    $2,178,134
                                                       ============    ===========    ============     ===========    ==========
</TABLE>

  The accompanying notes to financial statements are an integral part of this
                              financial statement.

                                        8
<PAGE>   10

<TABLE>
<CAPTION>
                                                   FIDELITY                                               THE GEORGE     FIDELITY
                                     VANGUARD      GROWTH &   T. ROWE PRICE  T. ROWE PRICE   EUROPACIFIC    PUTNAM      RETIREMENT
                                    U.S. GROWTH     INCOME      NEW INCOME      MID-CAP        GROWTH       FUND OF        MONEY
                                     PORTFOLIO    PORTFOLIO        FUND       GROWTH FUND       FUND        BOSTON A      MARKET
                                    -----------   ---------   -------------  -------------  -----------   -----------   -----------
YEAR ENDED DECEMBER 31, 1998        (PARTICIPANT DIRECTED; SEE NOTE 1)
- ----------------------------        ------------------------------------------------------------------------------------------------
<S>                                <C>           <C>           <C>          <C>           <C>          <C>          <C>
Additions to net assets
  attributed to:
  Investment income
    Net appreciation
      (depreciation)
      in market value of
        investments.............   $  670,827    $  890,582    $  (38,252)    $  273,536    $  140,946    $   18,498    $        --
    Interest....................       11,068        13,084         3,621          6,782         6,032        15,351         22,950
    Dividends...................      233,851       275,020        97,329         37,887        97,579       511,805        469,628
                                   ----------    ----------    ----------     ----------    ----------    ----------    -----------
      Total investment income
        (loss)..................      915,746     1,178,686        62,698        318,205       244,557       545,654        492,578
                                   ----------    ----------    ----------     ----------    ----------    ----------    -----------
  Contributions to the Plan
    By participants.............      573,324       689,069       224,952        264,321       296,175       400,805        760,678
    By the employer.............       27,190        33,379        10,280         13,073        13,692        34,405         63,133
                                   ----------    ----------    ----------     ----------    ----------    ----------    -----------
     Total contributions........      600,514       722,448       235,232        277,394       309,867       435,210        823,811
                                   ----------    ----------    ----------     ----------    ----------    ----------    -----------
     Total additions............    1,516,260     1,901,134       297,930        595,599       554,424       980,864      1,316,389
                                   ----------    ----------    ----------     ----------    ----------    ----------    -----------
Deductions from net assets
  attributed to:
  Benefits paid to
    participants................      (81,429)     (269,218)     (148,512)       (32,802)      (17,689)     (252,623)    (3,179,889)
                                   ----------    ----------    ----------     ----------    ----------    ----------    -----------
Transfers among funds and Plans:
  Net reallocations.............      333,755        72,952       356,102       (335,106)        5,640        22,742      2,603,617
  Loans to participants.........      (42,528)      (62,720)      (21,773)       (17,682)      (29,721)      (48,279)      (140,446)
  Loan repayments by
    participants................       39,744        58,608        10,895         25,413        27,703        57,052         86,346
                                   ----------    ----------    ----------     ----------    ----------    ----------    -----------
     Net transfers among funds
       and  Plans...............      330,971        68,840       345,224       (327,375)        3,622        31,515      2,549,517
                                   ----------    ----------    ----------     ----------    ----------    ----------    -----------
     Total deductions and net
       transfers among funds
       and Plans................      249,542      (200,378)      196,712       (360,177)      (14,067)     (221,108)      (630,372)
                                   ----------    ----------    ----------     ----------    ----------    ----------    -----------
       Net increase (decrease)..    1,765,802     1,700,756       494,642        235,422       540,357       759,756        686,017
Net assets available for
  benefits
       Beginning of year........    2,009,588     3,670,545       967,810      1,593,730     1,351,470     4,898,055      9,333,344
                                   ----------    ----------    ----------     ----------    ----------    ----------    -----------
       End of year..............   $3,775,390    $5,371,301    $1,462,452     $1,829,152    $1,891,827    $5,657,811    $10,019,361
                                   ==========    ==========    ==========     ==========    ==========    ==========    ===========
</TABLE>
<PAGE>   11

<TABLE>
<CAPTION>
                                                   FIDELITY                                 TEMPLETON
                                      SPARTAN     LOW-PRICED     FRANKLIN        PUTNAM     DEVELOPING  T. ROWE PRICE
                                    U.S. EQUITY     STOCK        SMALL CAP      VOYAGER      MARKETS      DIVIDEND     PARTICIPANTS'
                                    INDEX FUND       FUND      GROWTH FUND I     FUND A      TRUST I     GROWTH FUND   LOAN ACCOUNT
YEAR ENDED DECEMBER 31, 1998        -----------   ----------   -------------    -------     ----------  -------------  -------------
- ----------------------------        -------------------------------------------------------------------------------
<S>                                <C>           <C>          <C>             <C>          <C>          <C>            <C>
Additions to net assets
  attributed to:
  Investment income
    Net appreciation
      (depreciation)
      in market value of
        investments.............    $  329,934    $ (28,609)     $ 12,977      $  109,462    $(43,884)     $ 47,082     $        --
    Interest....................         5,516          420         1,258           1,421         734         1,035              --
    Dividends...................        31,778       34,748         7,777          73,542       4,571        31,809              --
                                    ----------    ---------      --------      ----------    --------      --------     -----------
      Total investment income
        (loss)..................       367,228        6,559        22,012         184,425     (38,579)       79,926              --
                                    ----------    ---------      --------      ----------    --------      --------     -----------
  Contributions to the Plan
    By participants.............       250,241       91,370       124,072          99,374      65,747        56,997              --
    By the employer.............        12,994        5,048         6,042           6,764       3,718         4,178              --
                                    ----------    ---------      --------      ----------    --------      --------     -----------
     Total contributions........       263,235       96,418       130,114         106,138      69,465        61,175              --
                                    ----------    ---------      --------      ----------    --------      --------     -----------
     Total additions............       630,463      102,977       152,126         290,563      30,886       141,101              --
                                    ----------    ---------      --------      ----------    --------      --------     -----------
Deductions from net assets
  attributed to:
  Benefits paid to
    participants................       (32,988)      (1,671)      (15,437)         (1,418)       (696)      (17,064)       (108,614)
                                    ----------    ---------      --------      ----------    --------      --------     -----------
Transfers among funds and Plans:
  Net reallocations.............       202,779     (128,089)      (72,321)        350,099     (71,583)      256,772              --
  Loans to participants.........       (25,827)        (306)      (12,885)        (10,222)     (6,869)         (318)      3,610,800
  Loan repayments by
    participants................        17,560        2,363         5,486           8,451       2,298         4,737      (2,861,430)
                                    ----------    ---------      --------      ----------    --------      --------     -----------
     Net transfers among funds
       and  Plans...............       194,512     (126,032)      (79,720)        348,328     (76,154)      261,191         749,370
                                    ----------    ---------      --------      ----------    --------      --------     -----------
     Total deductions and net
       transfers among funds
       and Plans................       161,524     (127,703)      (95,157)        346,910     (76,850)      244,127         640,756
                                    ----------    ---------      --------      ----------    --------      --------     -----------
       Net increase (decrease)..       791,987      (24,726)       56,969         637,473     (45,964)      385,228         640,756
Net assets available for
  benefits
       Beginning of year........     1,078,413      461,447       493,800         464,047     251,115       303,102       7,316,739
                                    ----------    ---------      --------      ----------    --------      --------     -----------
       End of year..............    $1,870,400    $ 436,721      $550,769      $1,101,520    $205,151      $688,330     $ 7,957,495
                                    ==========    =========      ========      ==========    ========      ========     ===========
</TABLE>
<PAGE>   12

                               MERCK & CO., INC.

                    EMPLOYEE STOCK PURCHASE AND SAVINGS PLAN

                         NOTES TO FINANCIAL STATEMENTS

1. DESCRIPTION OF THE PLAN:

     The Merck & Co., Inc. Employee Stock Purchase and Savings Plan (the "Plan")
was designed to provide an easy, economical way for employees to become
stockholders of Merck & Co., Inc. (the "Company" or "Merck") as well as a
systematic means of saving and investing for the future. Generally, any regular
full-time, part-time, or temporary employee of the Company who is a U.S.
resident covered by a collective bargaining agreement providing for
participation in this Plan as defined by the Plan document, and has completed
one year of employment, is eligible to participate.

     The Plan is administered by a management committee appointed by the Chief
Executive Officer of the Company. All costs of administering the Plan are borne
by the Company.

     Participants should refer to the Summary Plan Description for a complete
description of benefits provided.

     The Plan is subject to the provisions of the Employee Retirement Income
Security Act of 1974 (ERISA).

     CONTRIBUTIONS

     Depending on the terms of the applicable collective bargaining agreements,
participants may contribute from 2% up to either 10% or 15% of their base pay
per pay period. In addition, the Company will match 50% of employee
contributions up to 6% of base pay per pay period, or contributions of a
predetermined dollar amount negotiated with each bargaining group, whichever is
less. Certain unions have negotiated to allow a percentage of Company matching
contributions to follow the direction of the participants' contributions.

     INVESTMENT OPTIONS

     Participants direct the investment of their contributions into any
investment option including the Merck Common Stock Fund (Participant directed).
Participants should refer to each investment fund's prospectus for a more
complete description of the risks and strategies associated with each fund.
Participants may change their investment options daily. The following is a brief
description of each option:

     Merck Common Stock Fund

     The Merck Common Stock Fund invests primarily in Merck common stock and a
small portion of money market instruments for liquidity. This liquidity allows
for daily trading in the fund. Ownership is measured in units rather than
shares. An investment in this option allows the participant to become a
stockholder and part owner of the Company. The value of the investment can go up
or down depending on general factors affecting the stock market and specific
factors affecting the Company's business. This is neither a mutual fund nor a
diversified or managed investment option. Investing in a non-diversified single
stock involves more investment risk than investing in a diversified fund.

     T. Rowe Price Blue Chip Growth Fund

     The T. Rowe Price Blue Chip Growth Fund seeks to provide long-term growth
of capital. The fund invests primarily (at least 65% of its assets) in common
stocks of large and medium-sized blue chip companies that have the potential for
above-average earnings growth and are well established in their respective
industries. The fund may also invest in convertible stocks and bonds, preferred
stocks, bonds and warrants. Up to 20% of assets (excluding reserves) may be
invested in foreign securities, which may be subject to currency risks and
political and sovereign risks of the home country.

                                       11
<PAGE>   13
                               MERCK & CO., INC.

                    EMPLOYEE STOCK PURCHASE AND SAVINGS PLAN

                  NOTES TO FINANCIAL STATEMENTS -- (CONTINUED)

     Fidelity Equity-Income Fund

     Funds are invested in income-producing equity securities. Normally, at
least 65% of the fund's assets will be invested in income producing equity
securities. The fund has the flexibility to invest the balance in all types of
domestic and foreign securities, including bonds.

     Vanguard U.S. Growth Portfolio

     The Vanguard U.S. Growth Portfolio seeks to provide long-term capital
growth by investing in equity securities of large, established U.S. companies
that have good growth records, strong market positions and have exhibited
long-term financial strength to provide potential long-term growth.

     Fidelity Growth & Income Portfolio

     Funds are invested primarily in U.S. and foreign stocks, focusing on those
that pay current dividends and offer potential growth of earnings such as common
stocks, convertible securities, preferred stocks and warrants.

     T. Rowe Price New Income Fund

     The T. Rowe Price New Income Fund is a bond fund that seeks to provide the
highest level of income consistent with preservation of capital by purchasing
securities that have been rated as investment-grade by Standard & Poor's,
Moody's or Fitch Investor Services. The fund invests at least 80% of its assets
in income-producing investment-grade debt securities including U.S. government
and agency securities, corporate bonds, bank obligations and utilities. The
fund's dollar-weighted average maturity is generally expected to be between four
and fifteen years.

     T. Rowe Price Mid-Cap Growth Fund

     The T. Rowe Price Mid-Cap Growth Fund seeks to provide long-term capital
appreciation by investing primarily in the stock of medium-sized (mid-cap)
growth companies that offer the potential for above-average earnings growth. The
fund focuses on companies that are no longer considered new or emerging, but are
well-established. It may also invest in convertible securities, warrants and
foreign securities, which are subject to greater risks.

     EuroPacific Growth Fund

     This fund seeks long-term capital growth by investing primarily in
securities of companies outside the United States. Normally, at least 65% of the
fund's total assets will be invested in Europe or the Pacific Basin. The Pacific
Basin is generally defined as those countries bordering the Pacific Ocean and
includes, but is not limited to Australia, Canada, Japan, Malaysia and
Singapore. The fund may also invest in convertible securities, debt and
government securities and preferred stock. Foreign investment, especially in
developing countries, involve greater risks and may offer greater potential.

     The George Putnam Fund of Boston A

     This fund seeks to provide a balanced investment comprised of a
well-diversified portfolio of stocks and bonds that will produce both capital
growth and current income. Normally, no more than 75% of the fund's assets will
be invested in common stocks and convertible securities.

                                       12
<PAGE>   14
                               MERCK & CO., INC.

                    EMPLOYEE STOCK PURCHASE AND SAVINGS PLAN

                  NOTES TO FINANCIAL STATEMENTS -- (CONTINUED)

     Fidelity Retirement Money Market

     Funds are invested in high-quality U.S. dollar-denominated money market
instruments of U.S. and foreign issuers. Normally, the fund intends to invest
more than 25% of its total assets in obligations of institutions in the
financial services industry.

     Spartan U.S. Equity Index Fund

     This fund seeks to provide investment results that correspond to the total
return performance of common stocks traded in the United States. Funds are
primarily invested in securities of the companies which comprise the S&P 500
Index.

     Fidelity Low-Priced Stock Fund

     This fund seeks capital appreciation by investing mainly in low-priced
domestic and foreign common stocks ($35 or less at time of purchase). Foreign
securities may involve a higher degree of risk. This fund charges a redemption
fee to discourage short-term buying and selling of fund shares. If fund shares
are sold after being held for less than 90 days, the fund will deduct a
redemption fee from participants' accounts equal to 1.5% of the value of the
shares sold.

     Franklin Small Cap Growth Fund I

     This fund seeks long-term capital growth by investing primarily in stocks
of companies with market capitalization of less than $1.5 billion at the time of
the investment. The fund tries to invest at least one-third of its assets in
stocks of companies with market capitalization of $550 million or less. Although
the fund's assets are invested primarily in small companies, it may invest up to
35% of its total assets in larger capitalized companies with strong growth
potential, in relatively well-known larger companies in mature industries with
potential for capital appreciation and in corporate debt securities, including
bonds, notes and debentures if deemed appropriate. The fund may also invest up
to 25% of its total assets in foreign securities, which may involve greater
risks.

     Effective January 1, 1999, the Franklin Small Cap Growth Fund I shares were
changed to Class A.

     Putnam Voyager Fund A

     This fund seeks capital appreciation by investing primarily in common
stocks of companies that have potential for capital appreciation which is
significantly greater than that of the market averages. The fund may also invest
in convertible bonds, convertible preferred stocks, warrants, preferred stocks,
money market instruments and debt securities. The fund may invest up to 20% of
its total assets in securities principally traded in foreign markets. Foreign
securities are subject to currency, political, financial or sovereign risks of
the issuer's home country.

     Templeton Developing Markets Trust I

     This fund seeks long-term capitalization by investing in equity securities
of emerging market countries. The fund may invest up to 35% of its total assets
in debt securities, including bonds, notes, debentures, commercial paper,
certificates of deposit, time deposits and bankers' acceptances. Foreign
investments may involve greater risks.

     Effective January 1, 1999, the Templeton Developing Markets Trust I shares
were changed to Class A.

                                       13
<PAGE>   15
                               MERCK & CO., INC.

                    EMPLOYEE STOCK PURCHASE AND SAVINGS PLAN

                  NOTES TO FINANCIAL STATEMENTS -- (CONTINUED)

     T. Rowe Price Dividend Growth Fund

     This fund seeks to provide increasing dividend income over time, long-term
capital appreciation and reasonable current income through investments primarily
in dividend-paying stocks. The fund may also invest in bonds and foreign
securities.

     VESTING

     Participants are immediately vested in their contributions, all Company
matching contributions, plus actual earnings thereon.

     PLAN TERMINATION

     Although it has not expressed any intent to do so, the Company has the
right under the Plan to discontinue its contributions at any time and to
terminate the Plan subject to the provisions of the Employee Retirement Income
Security Act of 1974.

     PARTICIPANTS' LOAN ACCOUNT

     Participants may borrow from their account balances with interest charged
at the prime rate plus 1%. Loan terms range from one to five years or up to
thirty years for the purchase of a primary residence. The minimum loan is $500
and the maximum loan is the lesser of $50,000 less the highest outstanding loan
balance during the one year period prior to the new loan application date, or
50% of the participant's account balance less any current outstanding loan
balance. Activity related to these borrowings is reflected in the Participants'
Loan Account column of the financial statements.

     BENEFITS PAID TO PARTICIPANTS

     In-service (which include hardship withdrawals) and termination
distributions are made throughout the year in accordance with applicable Plan
provisions. At December 31, 1998 and 1997, net assets available for benefits
included distributions in process of payment of $835,834 and $698,384,
respectively.

2.  SUMMARY OF ACCOUNTING POLICIES:

     The financial statements of the Plan have been prepared on the accrual
basis of accounting. The investments of the Plan are stated at quoted market
value. Dividend income is recorded on the ex-dividend date. The net appreciation
(depreciation) in market value of investments is based on the beginning of the
year market value or value at the time of purchase during the year and is
included in the statement of changes in net assets available for benefits.

     USE OF ESTIMATES

     The financial statements are prepared in conformity with generally accepted
accounting principles and, accordingly, include amounts that are based on
management's best estimates and judgments. Actual results could differ from
these estimates.

3.  INCOME TAXES:

     The Plan obtained a tax determination letter from the Internal Revenue
Service on September 18, 1995 indicating that it had been designed in accordance
with applicable sections of the Internal Revenue Code ("IRC"). The Plan was most
recently amended in July 1998. The Plan sponsor believes that the Plan is

                                       14
<PAGE>   16
                               MERCK & CO., INC.

                    EMPLOYEE STOCK PURCHASE AND SAVINGS PLAN

                  NOTES TO FINANCIAL STATEMENTS -- (CONTINUED)

designed and currently operated in compliance with the IRC. Therefore, no
provision for income taxes has been made.

4.  OTHER MATTERS:

     Net reallocations in 1998 of ($1,272,189) consist of transfers between the
Plan and the Merck & Co., Inc. Employee Savings and Security Plan for employees
who changed their status during the year.

5.  PARTY-IN-INTEREST:

     All party-in-interest transactions are set forth on the attached schedules.

6.  PROHIBITED TRANSACTIONS:

     There were no prohibited transactions during 1998.

7.  SUBSEQUENT EVENTS:

     Subsequent to year end, the Company match was increased from 50% of
employee contributions up to 5% of base pay, subject to a $60 monthly cap, to
50% of employee contributions up to 6% of base pay and the monthly cap of $60
for certain unions was eliminated. The Company also amended the investment for
Company matching contributions according to the following age parameters:

     Under age 50 -- 50% of Company matching contributions is invested in the
Merck Common Stock Fund (Non-participant directed) and 50% is invested in the
funds to which the participant is currently contributing (Participant directed).

     Age 50 and above -- Participants have the option to invest all Company
matching contributions in any of the available fund options (Participant
directed).

                                       15
<PAGE>   17

                                                           SCHEDULE I
                                                           EIN: 22-1109110
                                                           PLAN NO.: 004

                               MERCK & CO., INC.

                    EMPLOYEE STOCK PURCHASE AND SAVINGS PLAN

          ITEM 27a -- SCHEDULE OF ASSETS HELD FOR INVESTMENT PURPOSES

                               DECEMBER 31, 1998

<TABLE>
<CAPTION>
                                                                 NUMBER OF
                                                              UNITS/SHARES AT
             NAME OF ISSUER AND TITLE OF ISSUE                CLOSE OF PERIOD       COST       CURRENT VALUE
             ---------------------------------                ---------------   ------------   -------------
<S>                                                           <C>               <C>            <C>
Merck Common Stock Fund*....................................    12,173,650      $ 98,151,603   $306,880,503
T. Rowe Price Blue Chip Growth Fund.........................       489,337        11,338,153     14,973,705
Fidelity Equity-Income Fund.................................        39,174         1,786,245      2,176,087
Vanguard U.S. Growth Portfolio..............................       100,606         3,124,410      3,771,723
Fidelity Growth & Income Portfolio..........................       117,067         3,906,124      5,366,261
T. Rowe Price New Income Fund...............................       165,838         1,486,350      1,461,033
T. Rowe Price Mid-Cap Growth Fund...........................        53,620         1,505,814      1,827,382
EuroPacific Growth Fund.....................................        66,549         1,876,722      1,889,995
The George Putnam Fund of Boston A..........................       313,337         5,696,707      5,652,596
Fidelity Retirement Money Market............................     9,991,208         9,991,208     10,010,154
Spartan U.S. Equity Index Fund..............................        42,507         1,349,043      1,868,618
Fidelity Low-Priced Stock Fund..............................        19,092           466,768        436,243
Franklin Small Cap Growth Fund I............................        24,376           557,244        550,170
Putnam Voyager Fund A.......................................        50,205         1,006,299      1,100,487
Templeton Developing Markets Trust I........................        19,893           275,123        204,899
T. Rowe Price Dividend Growth Fund..........................        31,244           637,885        687,684
Participants' Loan Account (with interest rates
  ranging from 9.0% to 9.5%)................................            --         7,948,137      7,948,137
                                                                                ------------   ------------
        Total Investments...................................                    $151,103,835   $366,805,677
                                                                                ============   ============
</TABLE>

- ---------------
* Denotes a party-in-interest to the Plan.

                                       16
<PAGE>   18

                                                           SCHEDULE II
                                                           EIN: 22-1109110
                                                           PLAN NO.: 004

                               MERCK & CO., INC.

                    EMPLOYEE STOCK PURCHASE AND SAVINGS PLAN

               ITEM 27D -- SCHEDULE OF REPORTABLE TRANSACTIONS(a)

                      FOR THE YEAR ENDED DECEMBER 31, 1998

<TABLE>
<CAPTION>
                                                                                                     CURRENT
                                                                                                      VALUE
                                                       PURCHASE                      COST OF       OF ASSETS ON
IDENTITY OF PARTY INVOLVED AND DESCRIPTION OF ASSETS    PRICE      SELLING PRICE      ASSET      TRANSACTION DATE    NET GAIN
- ----------------------------------------------------  ----------   -------------   -----------   ----------------   -----------
<S>                                                   <C>          <C>             <C>           <C>                <C>
Merck Common Stock Fund*
    251 purchase transactions....................     $34,639,546   $       --     $34,639,546     $34,639,546      $        --
    249 sales transactions.......................             --    35,288,818      18,162,832      35,288,818       17,125,986
Fidelity Retirement Money Market
    208 purchase transactions....................     15,609,271            --      15,609,271      15,609,271               --
    202 sales transactions.......................             --    14,916,715      14,916,715      14,916,715               --
</TABLE>

- ---------------

(a) Reportable transactions are transactions that, individually or in the
    aggregate, exceed 5% of the Plan's net assets as of the beginning of the
    Plan year.

  * Denotes a party-in-interest to the Plan.

                                       17
<PAGE>   19

                                                                      EXHIBIT 23

                   CONSENT OF INDEPENDENT PUBLIC ACCOUNTANTS

     As independent public accountants, we hereby consent to the incorporation
by reference of our report dated May 7, 1999 included in the financial
statements and exhibits required by Form 11-K Annual Report for the Merck & Co.,
Inc. Employee Stock Purchase and Savings Plan into the Company's previously
filed Registration Statements on Form S-8 (Nos. 33-21087, 33-21088, 33-36101,
33-40177, 33-51235, 33-53463, 33-64273, 33-64665, 333-23293 and 333-23295), on
Form S-4 (No. 33-50667) and on Form S-3 (Nos. 33-60322, 33-39349, 33-51785,
33-57421, 333-17045, 333-36383 and 333-77569). It should be noted that we have
not audited any financial statements of the Plan subsequent to December 31, 1998
or performed any audit procedures subsequent to the date of our report.

                                            ARTHUR ANDERSEN LLP

New York, New York
June 10, 1999

<PAGE>   1

                                                                   EXHIBIT 99(C)

                       FINANCIAL STATEMENTS AND EXHIBITS
                      REQUIRED BY FORM 11-K ANNUAL REPORT
        PURSUANT TO SECTION 15(D) OF THE SECURITIES EXCHANGE ACT OF 1934

                           COMMISSION FILE NO. 1-3305

                             ---------------------

              MERCK PUERTO RICO EMPLOYEE SAVINGS AND SECURITY PLAN
                            (FULL TITLE OF THE PLAN)

                               MERCK & CO., INC.
                                  P.O. BOX 100
                   WHITEHOUSE STATION, NEW JERSEY 08889-0100
             (NAME OF ISSUER OF THE SECURITIES HELD PURSUANT TO THE
            PLAN AND THE ADDRESS OF ITS PRINCIPAL EXECUTIVE OFFICE)
<PAGE>   2

                    REPORT OF INDEPENDENT PUBLIC ACCOUNTANTS

To Merck Sharp & Dohme Quimica de Puerto Rico, Inc. and
Merck Sharp & Dohme (I.A.) Corp.:

     We have audited the accompanying statements of net assets available for
benefits of the Merck Puerto Rico Employee Savings and Security Plan (the
"Plan") as of December 31, 1998 and 1997 and the related statement of changes in
net assets available for benefits for the year ended December 31, 1998. These
financial statements and the schedules referred to below are the responsibility
of the Plan's management. Our responsibility is to express an opinion on these
financial statements and schedules based on our audits.

     We conducted our audits in accordance with generally accepted auditing
standards. Those standards require that we plan and perform the audit to obtain
reasonable assurance about whether the financial statements are free of material
misstatement. An audit includes examining, on a test basis, evidence supporting
the amounts and disclosures in the financial statements. An audit also includes
assessing the accounting principles used and significant estimates made by
management, as well as evaluating the overall financial statement presentation.
We believe that our audits provide a reasonable basis for our opinion.

     In our opinion, the financial statements referred to above present fairly,
in all material respects, the net assets available for benefits of the Plan as
of December 31, 1998 and 1997, and the changes in its net assets available for
benefits for the year ended December 31, 1998, in conformity with generally
accepted accounting principles.

     Our audits were performed for the purpose of forming an opinion on the
basic financial statements taken as a whole. The supplemental schedules of
assets held for investment purposes and reportable transactions are presented
for purposes of additional analysis and are not a required part of the basic
financial statements but are supplementary information required by the
Department of Labor's Rules and Regulations for Reporting and Disclosure under
the Employee Retirement Income Security Act of 1974. The fund information in the
statement of net assets available for benefits and the statement of changes in
net assets available for benefits is presented for purposes of additional
analysis rather than to present the net assets available for plan benefits and
changes in net assets available for plan benefits of each fund. The supplemental
schedules and fund information have been subjected to the auditing procedures
applied in the audit of the basic financial statements and, in our opinion, are
fairly stated in all material respects in relation to the basic financial
statements taken as a whole.

                                                  ARTHUR ANDERSEN LLP

San Juan, Puerto Rico
May 9, 1999

                                        1
<PAGE>   3

                               MERCK PUERTO RICO

                       EMPLOYEE SAVINGS AND SECURITY PLAN

                 STATEMENT OF NET ASSETS AVAILABLE FOR BENEFITS

<TABLE>
<CAPTION>
                                                                       MERCK COMMON STOCK FUND
                                                                   --------------------------------
                                                                   (NON-PARTICIPANT   (PARTICIPANT    T. ROWE PRICE    FIDELITY
                                                                    DIRECTED: SEE     DIRECTED: SEE     BLUE CHIP       EQUITY-
                                                        TOTAL          NOTE 1)           NOTE 1)       GROWTH FUND    INCOME FUND
                                                        -----      ----------------   -------------   -------------   -----------
DECEMBER 31, 1998
- ---------------------------------------------------                                                   -------------------------
<S>                                                  <C>           <C>                <C>             <C>             <C>
Assets:
  Investments at market value......................  $33,769,371      $9,666,965       $19,533,155      $827,723      $    42,001
                                                     -----------      ----------       -----------      --------      -----------
  Receivables
    Employer's contribution........................       24,537           5,420            15,492           741              130
    Participants' contributions....................       85,652              --            74,861         3,173              161
    Accrued interest and dividends.................      107,220          34,234            69,159            --               --
                                                     -----------      ----------       -----------      --------      -----------
      Total receivables............................      217,409          39,654           159,512         3,914              291
                                                     -----------      ----------       -----------      --------      -----------
Net assets available for benefits..................  $33,986,780      $9,706,619       $19,692,667      $831,637      $    42,292
                                                     ===========      ==========       ===========      ========      ===========
</TABLE>

  The accompanying notes to financial statements are an integral part of this
                              financial statement.

                                        2
<PAGE>   4

<TABLE>
<CAPTION>
                                                                   FIDELITY
                                                      VANGUARD     GROWTH &    T. ROWE PRICE   T. ROWE PRICE   EUROPACIFIC
                                                     U.S. GROWTH    INCOME      NEW INCOME        MID-CAP         GROWTH
                                                      PORTFOLIO    PORTFOLIO       FUND         GROWTH FUND        FUND
                                                     -----------   ---------   -------------   -------------   -----------
DECEMBER 31, 1998                                      (PARTICIPANT DIRECTED; SEE NOTE 1)
- --------------------------------------------------------------------------------------------------------------------------
<S>                                                  <C>           <C>         <C>             <C>             <C>
Assets:
  Investments at market value......................   $295,492     $539,595       $17,557        $171,008        $133,469
                                                      --------     --------       -------        --------        --------
  Receivables
    Employer's contribution........................        280          424            29             292             233
    Participants' contributions....................      1,133        2,068            67             656             512
    Accrued interest and dividends.................         --           --            --              --              --
                                                      --------     --------       -------        --------        --------
      Total receivables............................      1,413        2,492            96             948             745
                                                      --------     --------       -------        --------        --------
Net assets available for benefits..................   $296,905     $542,087       $17,653        $171,956        $134,214
                                                      ========     ========       =======        ========        ========
</TABLE>

<TABLE>
<CAPTION>
                                                     THE GEORGE    FIDELITY      SPARTAN      FIDELITY
                                                       PUTNAM     RETIREMENT   U.S. EQUITY   LOW-PRICED
                                                      FUND OF       MONEY         INDEX        STOCK
                                                      BOSTON A      MARKET        FUND          FUND
                                                     ----------   ----------   -----------   ----------
DECEMBER 31, 1998                                    (PARTICIPANT DIRECTED; SEE NOTE 1)
- -------------------------------------------------------------------------------------------------------
<S>                                                  <C>          <C>          <C>           <C>
Assets:
  Investments at market value......................   $159,288     $380,176     $201,400      $11,966
                                                      --------     --------     --------      -------
  Receivables
    Employer's contribution........................        184          927          132           56
    Participants' contributions....................        611        1,457          772           46
    Accrued interest and dividends.................         --           --           --           --
                                                      --------     --------     --------      -------
      Total receivables............................        795        2,384          904          102
                                                      --------     --------     --------      -------
Net assets available for benefits..................   $160,083     $382,560     $202,304      $12,068
                                                      ========     ========     ========      =======
</TABLE>






















                                        3
<PAGE>   5

<TABLE>
<CAPTION>
                                                                               TEMPLETON
                                                       FRANKLIN      PUTNAM    DEVELOPING   T. ROWE PRICE
                                                       SMALL CAP     VOYAGER    MARKETS       DIVIDEND      PARTICIPANTS'
                                                     GROWTH FUND I   FUND A     TRUST I      GROWTH FUND    LOAN ACCOUNT
                                                     -------------   -------   ----------   -------------   -------------
DECEMBER 31, 1998
- -------------------------------------------------------------------------------------------------------------------------
<S>                                                  <C>             <C>       <C>          <C>             <C>
Assets:
  Investments at market value......................     $13,149      $12,196     $7,270        $2,729        $1,754,232
                                                        -------      -------     ------        ------        ----------
  Receivables
    Employer's contribution........................          74           71         27            25                --
    Participants' contributions....................          50           47         28            10                --
    Accrued interest and dividends.................          --           --         --            --             3,827
                                                        -------      -------     ------        ------        ----------
      Total receivables............................         124          118         55            35             3,827
                                                        -------      -------     ------        ------        ----------
Net assets available for benefits..................     $13,273      $12,314     $7,325        $2,764        $1,758,059
                                                        =======      =======     ======        ======        ==========
</TABLE>

                                        4
<PAGE>   6

                               MERCK PUERTO RICO

                       EMPLOYEE SAVINGS AND SECURITY PLAN

                 STATEMENT OF NET ASSETS AVAILABLE FOR BENEFITS

<TABLE>
<CAPTION>
                                                                       MERCK COMMON STOCK FUND
                                                                   --------------------------------
                                                                   (NON-PARTICIPANT   (PARTICIPANT    T. ROWE PRICE    FIDELITY
                                                                    DIRECTED: SEE     DIRECTED: SEE     BLUE CHIP       EQUITY-
                                                        TOTAL          NOTE 1)           NOTE 1)       GROWTH FUND    INCOME FUND
                                                        -----      ----------------   -------------   -------------   -----------
DECEMBER 31, 1997
- ---------------------------------------------------                                                   -------------------------
<S>                                                  <C>           <C>                <C>             <C>             <C>
Assets:
  Investments at market value......................  $24,835,401      $6,993,525       $13,976,782      $571,614      $   273,159
                                                     -----------      ----------       -----------      --------      -----------
  Receivables
    Employer's contribution........................        8,576           1,921             5,299           300               43
    Participants' contributions....................       30,065              --            26,206         1,072              512
    Accrued interest and dividends.................       88,376          29,067            58,086            --               --
                                                     -----------      ----------       -----------      --------      -----------
      Total receivables............................      127,017          30,988            89,591         1,372              555
                                                     -----------      ----------       -----------      --------      -----------
Net assets available for benefits..................  $24,962,418      $7,024,513       $14,066,373      $572,986      $   273,714
                                                     ===========      ==========       ===========      ========      ===========
</TABLE>

  The accompanying notes to financial statements are an integral part of this
                              financial statement.

                                        5
<PAGE>   7
<TABLE>
<CAPTION>
                                                   FIDELITY
                                      VANGUARD     GROWTH &    T. ROWE PRICE    T. ROWE PRICE    EUROPACIFIC
                                    U.S. GROWTH    INCOME       NEW INCOME         MID-CAP          GROWTH
                                     PORTFOLIO    PORTFOLIO        FUND          GROWTH FUND         FUND
                                   ------------   ---------    -------------    -------------    -----------
                                     (PARTICIPANT DIRECTED; SEE NOTE 1)
                                   -----------------------------------------------------------------------------
<S>                                   <C>           <C>          <C>              <C>              <C>
Assets:
  Investments at market value ......  $112,653      $318,090        $11,848         $125,293         $90,947
                                      --------      --------        -------         --------         -------
  Receivables
    Employer's contribution ........        77           163              9              111              86
    Participants' contributions ....       211           596             22              235             171
    Accrued interest and dividends..        --            --             --               --              --
                                      --------      --------        -------         --------         -------
      Total receivables ............       288           759             31              346             257
                                      --------      --------        -------         --------         -------
Net assets available for benefits ..  $112,941      $318,849        $11,879         $125,639         $91,204
                                      ========      ========        =======         ========         =======

<CAPTION>
                                     THE GEORGE      FIDELITY       FIDELITY     SPARTAN       FIDELITY
                                       PUTNAM       RETIREMENT     RETIREMENT  U.S. EQUITY    LOW-PRICED
                                      FUND OF         MONEY        GOVERNMENT     INDEX         STOCK
                                      BOSTON A        MARKET      MONEY MARKET    FUND           FUND
                                     -----------    ----------    ------------ -----------    ----------

                                     -----------    -------------------------- -------------------------
<S>                                    <C>            <C>           <C>          <C>            <C>
Assets:
  Investments at market value ......    $133,881      $353,066        $  --       $58,343        $5,626
                                        --------      --------        -----       -------        ------
    Receivables
    Employer's contribution ........          77           412           --            51             9
    Participants' contributions ....         251           662           --           109            11
    Accrued interest and dividends..          --            --           --            --            --
                                        --------      --------        -----       -------        ------
       Total receivables ...........         328         1,074           --           160            20
                                        --------      --------        -----       -------        ------
Net assets available for benefits...    $134,209      $354,140        $  --       $58,503        $5,646
                                        ========      ========        =====       =======        ======
</TABLE>

                                        6
<PAGE>   8

<TABLE>
<CAPTION>
                                                            TEMPLETON
                                                            FRANKLIN       PUTNAM     DEVELOPING    T. ROWE PRICE
                                                            SMALL CAP      VOYAGER     MARKETS        DIVIDEND       PARTICIPANTS'
                                                          GROWTH FUND I    FUND A      TRUST I       GROWTH FUND     LOAN ACCOUNT
                                                          -------------    -------    ----------    -------------    -------------
                                                          ------------------------------------------------------------------------
<S>                                                         <C>              <C>        <C>           <C>             <C>
Assets:
  Investments at market value......................          $1,245         $800        $1,641           $--          $1,806,888
                                                             ------         ----        ------           ---          ----------
  Receivables
    Employer's contribution........................               9            9            --            --                  --
    Participants' contributions....................               2            2             3            --                  --
    Accrued interest and dividends.................              --           --            --            --               1,223
                                                             ------         ----        ------           ---          ----------
      Total receivables............................              11           11             3            --               1,223
                                                             ------         ----        ------           ---          ----------
Net assets available for benefits..................          $1,256         $811        $1,644           $--          $1,808,111
                                                             ======         ====        ======           ===          ==========
</TABLE>

                                        7
<PAGE>   9

                               MERCK PUERTO RICO

                       EMPLOYEE SAVINGS AND SECURITY PLAN

           STATEMENT OF CHANGES IN NET ASSETS AVAILABLE FOR BENEFITS

<TABLE>
<CAPTION>
                                                                           MERCK COMMON STOCK
                                                                                  FUND
                                                                      -----------------------------
                                                                          (NON-                                        FIDELITY
                                                                       PARTICIPANT    (PARTICIPANT    T. ROWE PRICE     EQUITY-
                                                                      DIRECTED; SEE   DIRECTED; SEE     BLUE CHIP       INCOME
                                                           TOTAL         NOTE 1)         NOTE 1)       GROWTH FUND       FUND
                                                        -----------   -------------   -------------   -------------   -----------
YEAR ENDED DECEMBER 31, 1998
- ------------------------------------------------------                                                -------------------------
<S>                                                     <C>           <C>             <C>             <C>             <C>
Additions to net assets attributed to:
  Investment income (loss)
    Net appreciation(depreciation)
      in market value of investments..................  $ 8,347,916    $ 2,659,334     $ 5,333,097      $163,492       $ 14,471
    Interest..........................................      161,776         63,397          80,414         6,831            618
    Dividends.........................................      489,996        127,134         250,333        13,124          8,021
                                                        -----------    -----------     -----------      --------       --------
      Total investment income(loss)...................    8,999,688      2,849,865       5,663,844       183,447         23,110
                                                        -----------    -----------     -----------      --------       --------
  Contributions to the Plan
    By participants...................................    3,289,370             --       2,654,100       130,452         20,633
    By the employer...................................      934,413        918,911          10,193         1,153            710
                                                        -----------    -----------     -----------      --------       --------
      Total contributions.............................    4,223,783        918,911       2,664,293       131,605         21,343
                                                        -----------    -----------     -----------      --------       --------
      Total additions.................................   13,223,471      3,768,776       8,328,137       315,052         44,453
                                                        -----------    -----------     -----------      --------       --------
Deductions from net assets attributed to:
  Benefits paid to participants.......................   (4,357,447)    (1,155,046)     (2,792,099)      (47,016)       (29,788)
                                                        -----------    -----------     -----------      --------       --------
Transfers among funds and Plans:
  Net reallocations...................................      158,338         27,963         179,373       (15,040)      (246,175)
  Loans to participants...............................           --       (371,499)       (520,607)      (32,356)        (3,682)
  Loan repayments by participants.....................           --        411,912         431,490        38,011          3,770
                                                        -----------    -----------     -----------      --------       --------
      Net transfers among funds and Plans.............      158,338         68,376          90,256        (9,385)      (246,087)
                                                        -----------    -----------     -----------      --------       --------
      Total deductions and net transfers
        among funds and Plans.........................   (4,199,109)    (1,086,670)     (2,701,843)      (56,401)      (275,875)
                                                        -----------    -----------     -----------      --------       --------
        Net increase(decrease)........................    9,024,362      2,682,106       5,626,294       258,651       (231,422)
Net assets available for benefits
        Beginning of year.............................   24,962,418      7,024,513      14,066,373       572,986        273,714
                                                        -----------    -----------     -----------      --------       --------
        End of year...................................  $33,986,780    $ 9,706,619     $19,692,667      $831,637       $ 42,292
                                                        ===========    ===========     ===========      ========       ========
</TABLE>

  The accompanying notes to financial statements are an integral part of this
                              financial statement.

                                        8
<PAGE>   10

<TABLE>
<CAPTION>
                                                             FIDELITY
                                                VANGUARD     GROWTH &    T. ROWE PRICE   T. ROWE PRICE   EUROPACIFIC
                                               U.S. GROWTH    INCOME      NEW INCOME        MID-CAP        GROWTH
                                                PORTFOLIO    PORTFOLIO       FUND         GROWTH FUND       FUND
                                               -----------   ---------   -------------   -------------   -----------
    YEAR ENDED DECEMBER 31, 1998                  (PARTICIPANT DIRECTED; SEE NOTE 1)
- -----------------------------------------------------------------------------------------------------------------------
<S>                                            <C>           <C>         <C>             <C>             <C>
Additions to net assets attributed to:
  Investment income (loss)
    Net appreciation(depreciation)
      in market value of investments.......     $ 40,564     $ 77,601       $  (476)       $ 26,525       $  8,931
    Interest...............................          764        2,987           141           1,497          1,181
    Dividends..............................       18,090       24,768         1,174           3,620          6,724
                                                --------     --------       -------        --------       --------
      Total investment income(loss)........       59,418      105,356           839          31,642         16,836
                                                --------     --------       -------        --------       --------
  Contributions to the Plan
    By participants........................       42,170       81,910         5,590          50,969         37,307
    By the employer........................          203          723            20             181            767
                                                --------     --------       -------        --------       --------
      Total contributions..................       42,373       82,633         5,610          51,150         38,074
                                                --------     --------       -------        --------       --------
      Total additions......................      101,791      187,989         6,449          82,792         54,910
                                                --------     --------       -------        --------       --------
Deductions from net assets attributed to:
  Benefits paid to participants............       (8,316)     (59,106)       (1,696)        (25,663)       (11,738)
                                                --------     --------       -------        --------       --------
Transfers among funds and Plans:
  Net reallocations........................       89,657       80,154           452         (10,822)        (4,743)
  Loans to participants....................       (2,475)     (10,507)           --          (4,988)          (992)
  Loan repayments by participants..........        3,307       24,708           569           4,998          5,573
                                                --------     --------       -------        --------       --------
      Net transfers among funds and Plans..       90,489       94,355         1,021         (10,812)          (162)
                                                --------     --------       -------        --------       --------
      Total deductions and net transfers
        among funds and Plans..............       82,173       35,249          (675)        (36,475)       (11,900)
                                                --------     --------       -------        --------       --------
        Net increase(decrease).............      183,964      223,238         5,774          46,317         43,010
Net assets available for benefits
        Beginning of year..................      112,941      318,849        11,879         125,639         91,204
                                                --------     --------       -------        --------       --------
        End of year........................     $296,905     $542,087       $17,653        $171,956       $134,214
                                                ========     ========       =======        ========       ========

<CAPTION>
                                                 THE GEORGE     FIDELITY      SPARTAN      FIDELITY
                                                   PUTNAM      RETIREMENT   U.S. EQUITY   LOW-PRICED
                                                  FUND OF        MONEY         INDEX        STOCK
                                                  BOSTON A       MARKET        FUND          FUND
                                                 -----------   ----------   -----------   ----------
   YEAR ENDED DECEMBER 31, 1998                                 (PARTICIPANT DIRECTED; SEE NOTE 1)
- ----------------------------------------------------------------------------------------------------
<S>                                              <C>           <C>          <C>           <C>
Additions to net assets attributed to:
  Investment income (loss)
    Net appreciation(depreciation)
      in market value of investments.......       $    111      $     --     $ 23,845      $  (555)
    Interest...............................          1,308         2,213          198           17
    Dividends..............................         14,561        18,546        1,961          758
                                                  --------      --------     --------      -------
      Total investment income(loss)........         15,980        20,759       26,004          220
                                                  --------      --------     --------      -------
  Contributions to the Plan
    By participants........................         29,698       174,666       25,701        7,141
    By the employer........................            107           515          704           47
                                                  --------      --------     --------      -------
      Total contributions..................         29,805       175,181       26,405        7,188
                                                  --------      --------     --------      -------
      Total additions......................         45,785       195,940       52,409        7,408
                                                  --------      --------     --------      -------
Deductions from net assets attributed to:
  Benefits paid to participants............        (13,450)     (137,470)     (16,602)      (1,175)
                                                  --------      --------     --------      -------
Transfers among funds and Plans:
  Net reallocations........................         (6,696)      (22,655)     106,895      $    --
  Loans to participants....................         (4,011)      (17,586)        (433)         (82)
  Loan repayments by participants..........          4,246        10,191        1,532          271
                                                  --------      --------     --------      -------
      Net transfers among funds and Plans..         (6,461)      (30,050)     107,994          189
                                                  --------      --------     --------      -------
      Total deductions and net transfers
        among funds and Plans..............        (19,911)     (167,520)      91,392         (986)
                                                  --------      --------     --------      -------
        Net increase(decrease).............         25,874        28,420      143,801        6,422
Net assets available for benefits
        Beginning of year..................        134,209       354,140       58,503        5,646
                                                  --------      --------     --------      -------
        End of year........................       $160,083      $382,560     $202,304      $12,068
                                                  ========      ========     ========      =======
</TABLE>

                                       9
<PAGE>   11

<TABLE>
<CAPTION>
                                                                             TEMPLETON
                                                  FRANKLIN      PUTNAM       DEVELOPING   T. ROWE PRICE
                                                  SMALL CAP     VOYAGER       MARKETS       DIVIDEND      PARTICIPANTS'
                                                GROWTH FUND I   FUND A        TRUST I      GROWTH FUND    LOAN ACCOUNT
 YEAR ENDED DECEMBER 31, 1998                   -------------   -------      ----------   -------------   -------------
- -------------------------------------------------------------------------------------------------------------------------
<S>                                             <C>             <C>           <C>           <C>           <C>
Additions to net assets attributed to:
  Investment income (loss)
    Net appreciation(depreciation)
      in market value of investments.......     $   725         $   928       $ (795)       $  118        $       --
    Interest...............................          43              55          112            --                --
    Dividends..............................         186             808          109            79                --
                                                -------         -------       ------        ------        ----------
      Total investment income(loss)........         954           1,791         (574)          197                --
                                                -------         -------       ------        ------        ----------
  Contributions to the Plan
    By participants........................      11,433          10,379        4,679         2,542                --
    By the employer........................          65              62           27            25                --
                                                -------         -------       ------        ------        ----------
      Total contributions..................      11,498          10,441        4,706         2,567                --
                                                -------         -------       ------        ------        ----------
      Total additions......................      12,452          12,232        4,132         2,764                --
                                                -------         -------       ------        ------        ----------
Deductions from net assets attributed to:
  Benefits paid to participants............        (802)           (931)        (192)           --           (56,357)
                                                -------         -------       ------        ------        ----------
Transfers among funds and Plans:
  Net reallocations........................         206              --        1,080            --           (21,311)
  Loans to participants....................          --            (170)        (112)           --           969,500
  Loan repayments by participants..........         161             372          773            --          (941,884)
                                                -------         -------       ------        ------        ----------
      Net transfers among funds and Plans..         367             202        1,741            --             6,305
                                                -------         -------       ------        ------        ----------
      Total deductions and net transfers
        among funds and Plans..............        (435)           (729)       1,549            --           (50,052)
                                                -------         -------       ------        ------        ----------
        Net increase(decrease).............      12,017          11,503        5,681         2,764           (50,052)
Net assets available for benefits
        Beginning of year..................       1,256             811        1,644            --         1,808,111
                                                -------         -------       ------        ------        ----------
        End of year........................     $13,273         $12,314       $7,325        $2,764        $1,758,059
                                                =======         =======       ======        ======        ==========
</TABLE>

                                       10
<PAGE>   12

                               MERCK PUERTO RICO

                       EMPLOYEE SAVINGS AND SECURITY PLAN

                         NOTES TO FINANCIAL STATEMENTS

 1. DESCRIPTION OF THE PLAN:

     The Merck Puerto Rico Employee Savings and Security Plan (the "Plan") is a
profit sharing plan designed to provide an opportunity for employees of Merck
Sharp & Dohme Quimica de Puerto Rico, Inc. and Merck Sharp & Dohme (I.A.) Corp.
(the "Companies") to become stockholders of Merck & Co., Inc. ("Merck") and to
encourage them to save on a regular basis by setting aside part of their
earnings. Regular full-time and part-time employees of the Companies, as defined
in the Plan document, who have completed at least one year of employment and are
not covered by a collective bargaining agreement, are eligible to enroll in the
Plan.

     The Plan is administered by the Employee Benefits Committee appointed by
the President of the Companies. All costs of administering the Plan are borne by
the Companies.

     Participants should refer to the Summary Plan Description for a complete
description of benefits provided.

     The Plan is subject to the provisions of the Employee Retirement Income
Security Act of 1974 (ERISA).

     CONTRIBUTIONS

     Participants may contribute from 2% up to 15% of their base pay, provided
that pre-tax contributions shall not exceed 10% of base compensation. In
addition, the Companies match 50% of employee contributions up to 5% of base pay
per pay period. The Companies' matching contributions are invested entirely in
the Merck Common Stock Fund (Non-participant directed) and may not be
reallocated into any other investment option.

     INVESTMENT OPTIONS

     Participants direct the investment of their contributions into any
investment option including the Merck Common Stock Fund (Participant directed).
Participants should refer to each investment fund's prospectus for a more
complete description of the risks and strategies associated with each fund.
Participants may change their investment options daily. The following is a brief
description of each option:

     Merck Common Stock Fund

     The Merck Common Stock Fund invests primarily in Merck common stock and a
small portion of money market instruments for liquidity. This liquidity allows
for daily trading in the fund. Ownership is measured in units rather than
shares. An investment in this option allows the participant to become a
stockholder and part owner of Merck. The value of the investment can go up or
down depending on general factors affecting the stock market and specific
factors affecting Merck's business. This is neither a mutual fund nor a
diversified or managed investment option. Investing in a non-diversified single
stock involves more investment risk than investing in a diversified fund.

     T. Rowe Price Blue Chip Growth Fund

     The T. Rowe Price Blue Chip Growth Fund seeks to provide long-term growth
of capital. The fund invests primarily (at least 65% of its assets) in common
stocks of large and medium-sized blue chip companies that have the potential for
above-average earnings growth and are well established in their respective
industries. The fund may also invest in convertible stocks and bonds, preferred
stocks, bonds and warrants. Up

                                       11
<PAGE>   13
                               MERCK PUERTO RICO

                       EMPLOYEE SAVINGS AND SECURITY PLAN

                  NOTES TO FINANCIAL STATEMENTS -- (CONTINUED)

to 20% of assets (excluding reserves) may be invested in foreign securities,
which may be subject to currency risks and political and sovereign risks of the
home country.

     Fidelity Equity-Income Fund

     Funds are invested in income-producing equity securities. Normally, at
least 65% of the fund's assets will be invested in income producing equity
securities. The fund has the flexibility to invest the balance in all types of
domestic and foreign securities, including bonds.

     Vanguard U.S. Growth Portfolio

     The Vanguard U.S. Growth Portfolio seeks to provide long-term capital
growth by investing in equity securities of large, established U.S. companies
that have good growth records, strong market positions and have exhibited
long-term financial strength to provide potential long-term growth.

     Fidelity Growth & Income Portfolio

     Funds are invested primarily in U.S. and foreign stocks, focusing on those
that pay current dividends and offer potential growth of earnings such as common
stocks, convertible securities, preferred stocks and warrants.

     T. Rowe Price New Income Fund

     The T. Rowe Price New Income Fund is a bond fund that seeks to provide the
highest level of income consistent with preservation of capital by purchasing
securities that have been rated as investment-grade by Standard & Poor's,
Moody's or Fitch Investor Services. The fund invests at least 80% of its assets
in income-producing investment-grade debt securities including U.S. government
and agency securities, corporate bonds, bank obligations and utilities. The
fund's dollar-weighted average maturity is generally expected to be between four
and fifteen years.

     T. Rowe Price Mid-Cap Growth Fund

     The T. Rowe Price Mid-Cap Growth Fund seeks to provide long-term capital
appreciation by investing primarily in the stock of medium-sized (mid-cap)
growth companies that offer the potential for above-average earnings growth. The
fund focuses on companies that are no longer considered new or emerging, but are
well-established. It may also invest in convertible securities, warrants and
foreign securities, which are subject to greater risks.

     EuroPacific Growth Fund

     This fund seeks long-term capital growth by investing primarily in
securities of companies outside the United States. Normally, at least 65% of the
fund's total assets will be invested in Europe or the Pacific Basin. The Pacific
Basin is generally defined as those countries bordering the Pacific Ocean and
includes, but is not limited to Australia, Canada, Japan, Malaysia and
Singapore. The fund may also invest in convertible securities, debt and
government securities and preferred stock. Foreign investments, especially in
developing countries, involve greater risks and may offer greater potential.

                                       12
<PAGE>   14
                               MERCK PUERTO RICO

                       EMPLOYEE SAVINGS AND SECURITY PLAN

                  NOTES TO FINANCIAL STATEMENTS -- (CONTINUED)

     The George Putnam Fund of Boston A

     This fund seeks to provide a balanced investment comprised of a
well-diversified portfolio of stocks and bonds that will produce both capital
growth and current income. Normally, no more than 75% of the fund's assets will
be invested in common stocks and convertible securities.

     Fidelity Retirement Money Market

     Funds are invested in high-quality U.S. dollar-denominated money market
instruments of U.S. and foreign issuers. Normally, the fund intends to invest
more than 25% of its total assets in obligations of institutions in the
financial services industry.

     Spartan U.S. Equity Index Fund

     This fund seeks to provide results that correspond to the total return
performance of common stocks traded in the United States. Funds are primarily
invested in securities of the companies which comprise the S&P 500 Index.

     Fidelity Low-Priced Stock Fund

     This fund seeks capital appreciation by investing mainly in low-priced
domestic and foreign common stocks ($35 or less at time of purchase). Foreign
securities may involve a higher degree of risk. This fund charges a redemption
fee to discourage short-term buying and selling of fund shares. If fund shares
are sold after being held for less than 90 days, the fund will deduct a
redemption fee from participants' accounts equal to 1.5% of the value of the
shares sold.

     Franklin Small Cap Growth Fund I

     This fund seeks long-term capital growth by investing primarily in stocks
of companies with market capitalization of less than $1.5 billion at the time of
the investment. Although the fund's assets are invested primarily in small
companies, it may invest up to 35% of its total assets in larger capitalized
companies with strong growth potential, in relatively well-known larger
companies in mature industries with potential for capital appreciation, and in
corporate debt securities, including bonds, notes and debentures if deemed
appropriate. The fund may also invest up to 25% of its total assets in foreign
securities, which may involve greater risks.

     Effective January 1, 1999, the Franklin Small Cap Growth Fund I shares were
changed to Class A.

     Putnam Voyager Fund A

     This fund seeks capital appreciation by investing primarily in common
stocks of companies that have potential for capital appreciation which is
significantly greater than that of the market averages. The fund may also invest
in convertible bonds, convertible preferred stocks, warrants, preferred stocks,
money market instruments and debt securities. The fund may invest up to 20% of
its total assets in securities principally traded in foreign markets. Foreign
securities are subject to currency, political, financial or sovereign risks of
the issuer's home country.

     Templeton Developing Markets Trust I

     This fund seeks long-term capitalization by investing in equity securities
of emerging market countries. The fund may invest up to 35% of its total assets
in debt securities, including bonds, notes, debentures,
                                       13
<PAGE>   15
                               MERCK PUERTO RICO

                       EMPLOYEE SAVINGS AND SECURITY PLAN

                  NOTES TO FINANCIAL STATEMENTS -- (CONTINUED)

commercial paper, certificates of deposit, time deposits and bankers'
acceptances. Foreign investments may involve greater risks.

     Effective January 1, 1999 the Templeton Developing Markets Trust I shares
were changed to Class A.

     T. Rowe Price Dividend Growth Fund

     This fund seeks to provide increasing dividend income over time, long-term
capital appreciation and reasonable current income through investments primarily
in dividend-paying stocks. The fund may also invest in bonds and foreign
securities.

     VESTING

     Participants are immediately vested in their contributions, all Companies'
matching contributions, plus actual earnings thereon.

     PLAN TERMINATION

     Although they have not expressed any intent to do so, the Companies have
the right under the Plan to discontinue contributions at any time and to
terminate the Plan subject to the provisions of the Employee Retirement Income
Security Act of 1974.

     PARTICIPANTS' LOAN ACCOUNT

     Participants may borrow from their account balances with interest charged
at the prime rate plus 1%. Loan terms range from one to five years or up to
thirty years for the purchase of a primary residence. The minimum loan is $500
and the maximum loan is the lesser of $50,000 less the highest outstanding loan
balance during the one year period prior to the new loan application date, or
50% of the participant's account balance less any current outstanding loan
balance. Activity related to these borrowings is reflected in the Participants'
Loan Account column of the financial statements.

     BENEFITS

     Participants are entitled to receive automatic, voluntary, in-service
(which include hardship withdrawals), or mandatory distributions as provided in
the applicable Plan provisions.

 2. SUMMARY OF ACCOUNTING POLICIES:

     The financial statements of the Plan have been prepared on the accrual
basis of accounting. The investments of the Plan are stated at quoted market
value. Dividend income is recorded on the ex-dividend date. The net appreciation
(depreciation) in market value of investments is based on the beginning of the
year market value or value at the time of purchase during the year and is
included in the statement of changes in net assets available for benefits.

     USE OF ESTIMATES

     The financial statements are prepared in conformity with generally accepted
accounting principles and, accordingly, include amounts that are based on
management's best estimates and judgments. Actual results could differ from
these estimates.

                                       14
<PAGE>   16
                               MERCK PUERTO RICO

                       EMPLOYEE SAVINGS AND SECURITY PLAN

                  NOTES TO FINANCIAL STATEMENTS -- (CONTINUED)

 3. INCOME TAXES:

     The Plan obtained a tax determination letter from the Puerto Rico
Department of Treasury on February 18, 1998 indicating that it had been designed
in accordance with applicable sections of the Puerto Rico Internal Revenue Code
of 1994 ("PRIRC"). The Plan sponsors believe that the Plan is designed and
operated in compliance with the PRIRC. The Plan sponsors also believe that the
Plan is designed and currently operated as a qualified plan under the United
States Internal Revenue Code. The Plan has not been amended since its inception
on July 1, 1997. A favorable determination letter was received from the Internal
Revenue Service in November, 1998. Therefore, no provision for income taxes has
been made.

 4. OTHER MATTERS:

     Net reallocations in 1998 of $158,338 consist of transfers between the Plan
and the Merck & Co., Inc. Employee Savings and Security Plan for employees who
changed their status during the year.

 5. PARTY-IN-INTEREST:

     All party-in-interest transactions are set forth on the attached schedules.

 6. PROHIBITED TRANSACTIONS:

     There were no prohibited transactions during 1998.

                                       15
<PAGE>   17

                                                           SCHEDULE I
                                                           EIN:  66-0288298
                                                           PLAN NO.:  061

                               MERCK PUERTO RICO

                       EMPLOYEE SAVINGS AND SECURITY PLAN

          ITEM 27A -- SCHEDULE OF ASSETS HELD FOR INVESTMENT PURPOSES

                               DECEMBER 31, 1998

<TABLE>
<CAPTION>
                                                                NUMBER OF
                                                             UNITS/SHARES AT
             NAME OF ISSUER AND TITLE OF ISSUE               CLOSE OF PERIOD         COST          CURRENT VALUE
             ---------------------------------               ---------------      -----------      -------------
<S>                                                          <C>                  <C>              <C>
Merck Common Stock Fund*....................................    1,160,425         $12,289,885       $29,200,120
T. Rowe Price Blue Chip Growth Fund.........................       27,050             633,492           827,723
Fidelity Equity Income Fund.................................          756              39,435            42,001
Vanguard U.S. Growth Portfolio..............................        7,882             254,117           295,492
Fidelity Growth & Income Portfolio..........................       11,771             458,751           539,595
T. Rowe Price New Income Fund...............................        1,993              17,803            17,557
T. Rowe Price Mid-Cap Growth Fund...........................        5,018             138,771           171,008
EuroPacific Growth Fund.....................................        4,700             133,508           133,469
The George Putnam Fund of Boston A..........................        8,830             160,765           159,288
Fidelity Retirement Money Market............................      380,175             380,175           380,176
Spartan U.S. Equity Index Fund..............................        4,581             175,925           201,400
Fidelity Low-Priced Stock Fund..............................          524              12,519            11,966
Franklin Small Cap Growth Fund 1............................          583              12,602            13,149
Putnam Voyager Fund A.......................................          557              11,292            12,196
Templeton Developing Markets Trust 1........................          706               8,415             7,270
T. Rowe Price Dividend Growth Fund..........................          124               2,611             2,729
Participants' Loan Account (with interest rates ranging from
  9.5% to 9.5%).............................................           --           1,754,232         1,754,232
                                                                                  -----------       -----------
        Total Investments...................................                      $16,484,298       $33,769,371
                                                                                  ===========       ===========
</TABLE>

- ---------------
* Denotes a party-in-interest to the Plan.

                                       16
<PAGE>   18

                                                           SCHEDULE II
                                                           EIN:  66-0288298
                                                           PLAN NO.:  061

                               MERCK PUERTO RICO

                       EMPLOYEE SAVINGS AND SECURITY PLAN

               ITEM 27D -- SCHEDULE OF REPORTABLE TRANSACTIONS(A)

                      FOR THE YEAR ENDED DECEMBER 31, 1998

<TABLE>
<CAPTION>
                                                                                                  CURRENT
                                                                                                   VALUE
                                                        PURCHASE     SELLING      COST OF       OF ASSETS ON
IDENTITY OF PARTY INVOLVED AND DESCRIPTION OF ASSETS     PRICE        PRICE        ASSET      TRANSACTION DATE    NET GAIN
- ----------------------------------------------------   ----------   ----------   ----------   ----------------   ----------
<S>                                                    <C>          <C>          <C>          <C>                <C>
Merck Common Stock Fund*
    135 purchase transactions.....................     $5,103,922   $       --   $5,103,922      $5,103,922      $       --
     64 sales transactions........................             --    4,869,142    2,881,161       4,869,142       1,987,981
</TABLE>

- ---------------
(a) Reportable transactions are transactions that, individually or in the
    aggregate, exceed 5% of the Plan's net assets as of the beginning of the
    Plan year.

*Denotes a party-in-interest to the Plan.
>

                                       17
<PAGE>   19

                                                                      EXHIBIT 23

                   CONSENT OF INDEPENDENT PUBLIC ACCOUNTANTS

     As independent public accountants, we hereby consent to the incorporation
by reference of our report dated May 9, 1999 included in the financial
statements and exhibits required by Form 11-K Annual Report for the Merck Puerto
Rico Employee Savings and Security Plan into the previously filed Registration
Statements of Merck & Co., Inc. on Form S-8 (Nos. 33-21087, 33-21088, 33-36101,
33-40177, 33-51235, 33-53463, 33-64273, 33-64665, 333-23293 and 333-23295), on
Form S-4 (No. 33-50667) and on Form S-3 (Nos. 33-60322, 33-39349, 33-51785,
33-57421, 333-17045, 333-36383 and 333-77569). It should be noted that we have
not audited any financial statements of the Plan subsequent to December 31, 1998
or performed any audit procedures subsequent to the date of our report.

                                            ARTHUR ANDERSEN LLP

San Juan, Puerto Rico
June 10, 1999


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