• Dr. Bartosz Helfer, PhD, MSc
Assistant Professor, Director, Meta-Research Centre, University of Wroclaw, Poland
National Heart and Lung Institute, Imperial College London, UK; and
• Dr. David L. Steiner, PhD, CPsych
Professor Emeritus, Department of Psychiatry and Behavioural Neurosciences,
McMaster University
102. The NNE Paper includes an Abstract at the outset that summarizes the background for
the study, methods used, findings together with a conclusion. Given the importance of the NNE
Paper to the Union position I set the Abstract out in its entirety:
Abstract
Background: Vaccine mandates and vaccine passports (VMVP) for SARS-CoV-2 are thought to
be a path out of the pandemic by increasing vaccination through coercion and excluding
unvaccinated people from different settings because they are viewed as being at significant risk
of transmitting SARS-CoV-2. While variants and waning efficacy are relevant, SARS-CoV-2
vaccines reduce the risk of infection, transmission, and severe illness/hospitalization in adults.
Thus, higher vaccination levels are beneficial by reducing healthcare system pressures and
societal fear. However, the benefits of excluding unvaccinated people are unknown.
Methods: A method to evaluate the benefits of excluding unvaccinated people to reduce
transmissions is described, called the number need to exclude (NNE). The NNE is analogous to
the number needed to treat (NNT=1/ARR), except the absolute risk reduction (ARR) is the
baseline transmission risk in the population for a setting (e.g. healthcare). The rationale for the
NNE is that exclusion removes all unvaccinated people from a setting, such that the ARR is the
baseline transmission risk for that type of setting, which depends on the secondary attack rate
(SAR) typically observed in that type of setting and the baseline infection risk in the population.
The NNE is the number of unvaccinated people who need to be excluded from a setting to
prevent one transmission event from unvaccinated people in that type of setting. The NNE
accounts for the transmissibility of the currently dominant Delt (B.1.617.2) variant to estimate
the minimum NNE in six types of settings: households, social gatherings, casual close contacts,
work/study places, healthcare, and travel/transportation. The NNE can account for future
potentially dominant variants (e.g., Omicron, B.1.1.529). Th assist societies and policymakers in
their decision-making about VMVP, the NNEs were calculated using the current (mid-to-end
November 2021) baseline infection risk in many countries.
Findings: The NNEs suggest that at least 1,000 unvaccinated people likely need to be excluded
to prevent one SARS-CoV-2 transmission event in most types of settings for many jurisdictions,
notably Australia, California, Canada, China, France, Israel, and others. The NNEs of almost
every jurisdiction examined are well within the ranged of the NNTs of acetylsalicylic acid (ASA)
in primary prevention of cardiovascular disease (CVD) (> 250 to 333). This is important since
ASA is not recommended for primary prevention of CVD because the harms outweigh the
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