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Early effectiveness of Pfizer Covid-19 vaccine in preventing SARSCoV-2 infection in healthcare personnel in six Israeli hospitals

Joseph (Yossi) Levy, Ph.D,
Senior biostatistician & data scientist



Mass vaccination is considered the most important strategy to achieve sustained mitigation of the threat posed by Covid-19, by preventing morbidity and mortality and reducing SARS CoV-2 transmission.


At the beginning of 2021 we conducted a prospective cohort study, designed to evaluate the effectiveness of the Covid-19 vaccine in preventing SARS-CoV-2 infections among Healthcare personnel in 6 Clalit hospitals in Israel. To optimize the chances of detecting asymptomatic infections and identifying all symptomatic infections, each participant had a weekly PCR as serological tests during 12 weeks of follow-up.


The main study result was that the adjusted vaccine effectiveness was 94.5%. The results show evidence for vaccine efficacy, even in a more susceptible environment such as hospitals. In light of the results, the public in Israel that has not yet been vaccinated was further encouraged by policy makers to get the vaccination.


Reference: Katz, Mark A., et al. "Early effectiveness of BNT162b2 Covid-19 vaccine in preventing SARS-CoV-2 infection in healthcare personnel in six Israeli hospitals (CoVEHPI)." Vaccine 40.3 (2022): 512-520.‏

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