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What do we know about covid vaccines and preventing transmission?

BMJ 2022; 376 doi: (Published 04 February 2022) Cite this as: BMJ 2022;376:o298

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Rapid Response:

Re: Response to Chris Stokel-Walker on Why do policymakers still debate mandates if vaccines are not good at preventing transmission?

Dear Editor

Prior to vaccine rollout, it was already pointed out that Pfizer and Moderna’s claim that their vaccines were “95% effective” was based solely “on the trials’ primary endpoint of covid-19 of essentially any severity, and importantly not the vaccine’s ability to save lives, nor the ability to prevent infection, nor the efficacy in important subgroups (e.g. frail elderly).” [1]

Also the “US Food and Drug Administration listed important remaining unknowns in its review in December 2020: whether covid-19 vaccines reduce the risk of hospital admission, intensive care unit admission, severe covid-19, and mortality, as well as whether the vaccines are effective in populations at high risk of severe covid-19” [2]. Ongoing transmission in countries with high levels of vaccination challenge the belief that the covid-19 vaccines prevent infection and transmission at any clinically meaningful level [3].

Stokel-Walker’s interpretation that these hastily developed and rolled out vaccines against covid-19 have helped to prevent infection, illness, hospital admission, and death must be subject to a rigorous debate.
It is puzzling that, on the one hand the vaccines are assumed to be 95% effective to reduce covid-19 of essentially any severity, but on the other hand we are now told, that preventing transmission and infection was not a primary goal of vaccinating against covid-19 [4]. Firstly, this undermines the pressure put on the unvaccinated, claiming that those individuals were somehow responsible for spreading the virus. Secondly, the call for vaccine mandates as the only way out of the pandemic cannot be justified either. In particular vaccine advocates early on postulated that effectiveness against SARS-CoV-2 would not wane over time and would work for different strains [5,6]. However, we learned from the latest UK Covid-19 surveillance report that vaccine effectiveness is clearly fading away over a six months period and against the omicron variant [7].

Promises related to the conditional approval of the vaccines and the ensuing vaccination campaigns such as “our life will soon turn back to normal”, covid-19 vaccines will prevent hospitalisation, will prevent death, will grant sterile immunity plus vaccinated people are not infectious and not susceptible for infection, do not hold.

Why then should an individual with normal risk of covid-19 be forced to get vaccinated by nation wide vaccine mandates? “To protect the vulnerable” obviously cannot be achieved by a vaccine that does not prevent transmission.

[1] Doshi P. Pfizer and Moderna`s “95% effective” vaccines – let`s be cautious and first see the full data. (accessed February 13, 2022, at
[2] Prugger C et al. Evaluating covid-19 vaccine efficacy and safety in the post-authorisation phase. BMJ 2021; 375:e067570.
[3] Franco-Paredes C. Transmissibility of SARS-CoV-2 among fully vaccinated individuals. Lancet Infectious Diseases 2022; 22: 16 (21) 00768-4
[4] Stokel-Walker C. What do we know about covid vaccines and preventing transmission? BMJ 2022:376:o298
[5] Dejnirattisai W et al. Antibody evasion by the P.1 strain of SARS-CoV-2. Cell 2021; 184:2939-2945
[6] Robert Koch Institut. Welchen Einfluss haben die neuen Varianten von SARS-CoV-2 auf die Wirksamkeit der covid-19 Impfstoffe? RKI 24.1.2022. (accessed February 14, 2022)
[7] UK Health Security Agency. Covid-19 vaccine surveillance report: week 6, February 10, 2022.

Competing interests: No competing interests

15 February 2022
Ulrich Keil
Professor of Epidemiology and Social Medicine
Angela Spelsberg (Epidemiologist. Comprehensive Cancer Centre Aachen e.V., Aachen, Germany)
University of Muenster, Muenster, Germany
Albert Schweitzer Campus 1, 48149 Muenster, Germany