A study conducted in Israel evaluated the effectiveness of the BNT162b2 mRNA vaccine against Covid-19 in a nationwide mass vaccination setting. The study analyzed data from Clalit Health Services, the largest healthcare organization in Israel, and included 596,618 individuals who received the vaccine between December 20, 2020, and February 1, 2021. These individuals were matched with unvaccinated controls to assess vaccine effectiveness for various outcomes, including documented SARS-CoV-2 infection, symptomatic Covid-19, hospitalization, severe illness, and death. The study found that the vaccine was effective in preventing these outcomes. Vaccine effectiveness was estimated as one minus the risk ratio, using the Kaplan-Meier estimator. For documented infection, effectiveness was 46% (95% CI, 40 to 51) 14-20 days after the first dose and 92% (95% CI, 88 to 95) 7 or more days after the second dose. For symptomatic Covid-19, effectiveness was 57% (95% CI, 50 to 63) and 94% (95% CI, 87 to 98). For hospitalization, effectiveness was 74% (95% CI, 56 to 86) and 87% (95% CI, 55 to 100). For severe illness, effectiveness was 62% (95% CI, 39 to 80) and 92% (95% CI, 75 to 100). Estimated effectiveness in preventing death from Covid-19 was 72% (95% CI, 19 to 100) 14-20 days after the first dose. The study also found that vaccine effectiveness was consistent across age groups, with potentially slightly lower effectiveness in individuals with multiple coexisting conditions. The results are consistent with findings from randomized trials of the BNT162b2 vaccine. The study highlights the effectiveness of the vaccine in a real-world setting, with high effectiveness for preventing symptomatic Covid-19, hospitalization, severe illness, and death. The findings suggest that the BNT162b2 mRNA vaccine is effective for a wide range of Covid-19-related outcomes, supporting its use in mass vaccination campaigns.A study conducted in Israel evaluated the effectiveness of the BNT162b2 mRNA vaccine against Covid-19 in a nationwide mass vaccination setting. The study analyzed data from Clalit Health Services, the largest healthcare organization in Israel, and included 596,618 individuals who received the vaccine between December 20, 2020, and February 1, 2021. These individuals were matched with unvaccinated controls to assess vaccine effectiveness for various outcomes, including documented SARS-CoV-2 infection, symptomatic Covid-19, hospitalization, severe illness, and death. The study found that the vaccine was effective in preventing these outcomes. Vaccine effectiveness was estimated as one minus the risk ratio, using the Kaplan-Meier estimator. For documented infection, effectiveness was 46% (95% CI, 40 to 51) 14-20 days after the first dose and 92% (95% CI, 88 to 95) 7 or more days after the second dose. For symptomatic Covid-19, effectiveness was 57% (95% CI, 50 to 63) and 94% (95% CI, 87 to 98). For hospitalization, effectiveness was 74% (95% CI, 56 to 86) and 87% (95% CI, 55 to 100). For severe illness, effectiveness was 62% (95% CI, 39 to 80) and 92% (95% CI, 75 to 100). Estimated effectiveness in preventing death from Covid-19 was 72% (95% CI, 19 to 100) 14-20 days after the first dose. The study also found that vaccine effectiveness was consistent across age groups, with potentially slightly lower effectiveness in individuals with multiple coexisting conditions. The results are consistent with findings from randomized trials of the BNT162b2 vaccine. The study highlights the effectiveness of the vaccine in a real-world setting, with high effectiveness for preventing symptomatic Covid-19, hospitalization, severe illness, and death. The findings suggest that the BNT162b2 mRNA vaccine is effective for a wide range of Covid-19-related outcomes, supporting its use in mass vaccination campaigns.