• Noa Dagan, Noam Barda, Eldad Kepten, Oren Miron, Shay Perchik, Mark A Katz, Miguel A Hernán, Marc Lipsitch, Ben Reis, and Ran D Balicer.
• From the Clalit Research Institute, Innovation Division, Clalit Health Services, Tel Aviv (N.D., N.B., E.K., O.M., S.P., M.A.K., R.D.B.), and the School of Public Health, Faculty of Health Sciences, Ben Gurion University of the Negev, Be'er Sheva (O.M., M.A.K., R.D.B.) - both in Israel; University of Michigan School of Public Health, Ann Arbor (M.A.K.); and the Department of Biomedical Informatics (N.D., N.B.), Harvard Medical School (B.R.), the Departments of Epidemiology and Biostatistics (M.A.H.), and the Center for Communicable Disease Dynamics, Departments of Epidemiology and of Immunology and Infectious Diseases (M.L.), Harvard T.H. Chan School of Public Health, Harvard-MIT Division of Health Sciences and Technology (M.A.H.), and the Predictive Medicine Group, Computational Health Informatics Program, Boston Children's Hospital (B.R.) - all in Boston.
• N. Engl. J. Med. 2021 Apr 15; 384 (15): 141214231412-1423.

BackgroundAs mass vaccination campaigns against coronavirus disease 2019 (Covid-19) commence worldwide, vaccine effectiveness needs to be assessed for a range of outcomes across diverse populations in a noncontrolled setting. In this study, data from Israel's largest health care organization were used to evaluate the effectiveness of the BNT162b2 mRNA vaccine.MethodsAll persons who were newly vaccinated during the period from December 20, 2020, to February 1, 2021, were matched to unvaccinated controls in a 1:1 ratio according to demographic and clinical characteristics. Study outcomes included documented infection with the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), symptomatic Covid-19, Covid-19-related hospitalization, severe illness, and death. We estimated vaccine effectiveness for each outcome as one minus the risk ratio, using the Kaplan-Meier estimator.ResultsEach study group included 596,618 persons. Estimated vaccine effectiveness for the study outcomes at days 14 through 20 after the first dose and at 7 or more days after the second dose was as follows: for documented infection, 46% (95% confidence interval [CI], 40 to 51) and 92% (95% CI, 88 to 95); for symptomatic Covid-19, 57% (95% CI, 50 to 63) and 94% (95% CI, 87 to 98); for hospitalization, 74% (95% CI, 56 to 86) and 87% (95% CI, 55 to 100); and for severe disease, 62% (95% CI, 39 to 80) and 92% (95% CI, 75 to 100), respectively. Estimated effectiveness in preventing death from Covid-19 was 72% (95% CI, 19 to 100) for days 14 through 20 after the first dose. Estimated effectiveness in specific subpopulations assessed for documented infection and symptomatic Covid-19 was consistent across age groups, with potentially slightly lower effectiveness in persons with multiple coexisting conditions.ConclusionsThis study in a nationwide mass vaccination setting suggests that the BNT162b2 mRNA vaccine is effective for a wide range of Covid-19-related outcomes, a finding consistent with that of the randomized trial.Copyright © 2021 Massachusetts Medical Society.

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