The largest real-world study has found that the Pfizer vaccine is 94% effective at preventing COVID-19.
Researchers at The Clalit Research Institute and Harvard University have conducted the first real-world analysis of the efficacy of the Pfizer vaccine. This large-scale study took place in a nationwide mass-vaccination setting in Israel. At a time when Israel’s cases were at their peak and authorities were reporting almost 12,000 new cases per day. Researchers analyzed data from over 1 million people who had received the Pfizer vaccine between 20th December 2020 and 1st February 2021. They then matched them with unvaccinated controls according to their clinical characteristics and demographics.
Although randomized clinical trials are the ‘gold standard’ for evaluating vaccine efficacy, their highly controlled setting does not assess for all factors. Nor can one estimate vaccine efficacy in different subpopulations. The experimental design used for the real-world study allowed for a more detailed analysis of the vaccine’s effectiveness. Moreover, researchers could assess the vaccine’s efficacy across a range of subpopulations, age-groups, and outcomes. The study outcomes included documented infection, symptomatic COVID-19, severe disease, hospitalization, and death.
However, the study’s design did not allow for the assessment of asymptomatic infections or viral transmission in a mass-vaccination setting.
94% Effective at Preventing Infection
The results, published in the New England Journal of Medicine, further confirm the findings of Pfizer’s phase 3 clinical trials. The authors of the study report that the Pfizer vaccine is 94% effective against symptomatic infection, 92% against severe disease, and 97% against hospitalizations.
At the time of the study, the UK variant was prevalent in Israel and the results further prove the Pfizer vaccine’s effectiveness against the new variants. Therefore, the results further provide hope that COVID-19 vaccines can likely put an end to the pandemic.
Dagan, N., Barda, N., Kepten, E., Miron, O., Perchik, S., Katz, M. A., . . . Balicer, R. D. (2021). BNT162b2 mRNA Covid-19 vaccine in a nationwide mass Vaccination Setting. New England Journal of Medicine. doi:10.1056/nejmoa2101765