• Chandra J Cohen-Stavi, Ori Magen, Noam Barda, Shlomit Yaron, Alon Peretz, Doron Netzer, Carlo Giaquinto, Ali Judd, Leonard Leibovici, Miguel A Hernán, Marc Lipsitch, Ben Y Reis, Ran D Balicer, and Noa Dagan.
• From the Clalit Research Institute, Innovation Division (C.J.C.-S., O.M., R.D.B., N.D.), and the Community Medicine Division (S.Y., A.P., D.N.), Clalit Health Services, and the Faculty of Medicine, Tel-Aviv University (L.L.), Tel Aviv, the Research Authority, Rabin Medical Center, Petah-Tiqva (L.L.), the ARC (Accelerate Redesign Collaborate) Innovation Center, Chaim Sheba Medical Center at Tel HaShomer, Ramat-Gan (N.B.), Software and Information Systems Engineering (N.B., N.D.), and the School of Public Health (R.D.B.), Ben Gurion University of the Negev, Be'er Sheva, and the School of Public Health, University of Haifa, Haifa (A.P.) - all in Israel; the Departments of Biomedical Informatics (N.B., B.Y.R., N.D.) and Pediatrics (B.Y.R.), Harvard Medical School, CAUSALab, Departments of Epidemiology and Biostatistics (M.A.H.), and the Center for Communicable Disease Dynamics, Departments of Epidemiology and Immunology and Infectious Diseases (M.L.), Harvard T.H. Chan School of Public Health, the Ivan and Francesca Berkowitz Family Living Laboratory Collaboration, Harvard Medical School and Clalit Research Institute (B.Y.R., R.D.B., N.D.), and the Predictive Medicine Group, Computational Health Informatics Program, Boston Children's Hospital (B.Y.R.) - all in Boston; the Department of Women and Child Health, University of Padua, Padua, Italy (C.G.); and the Medical Research Council Clinical Trials Unit, University College London, London (A.J.).
• N. Engl. J. Med. 2022 Jul 21; 387 (3): 227236227-236.

BackgroundLimited evidence is available on the real-world effectiveness of the BNT162b2 vaccine against coronavirus disease 2019 (Covid-19) and specifically against infection with the omicron variant among children 5 to 11 years of age.MethodsUsing data from the largest health care organization in Israel, we identified a cohort of children 5 to 11 years of age who were vaccinated on or after November 23, 2021, and matched them with unvaccinated controls to estimate the vaccine effectiveness of BNT162b2 among newly vaccinated children during the omicron wave. Vaccine effectiveness against documented severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and symptomatic Covid-19 was estimated after the first and second vaccine doses. The cumulative incidence of each outcome in the two study groups through January 7, 2022, was estimated with the use of the Kaplan-Meier estimator, and vaccine effectiveness was calculated as 1 minus the risk ratio. Vaccine effectiveness was also estimated in age subgroups.ResultsAmong 136,127 eligible children who had been vaccinated during the study period, 94,728 were matched with unvaccinated controls. The estimated vaccine effectiveness against documented infection was 17% (95% confidence interval [CI], 7 to 25) at 14 to 27 days after the first dose and 51% (95% CI, 39 to 61) at 7 to 21 days after the second dose. The absolute risk difference between the study groups at days 7 to 21 after the second dose was 1905 events per 100,000 persons (95% CI, 1294 to 2440) for documented infection and 599 events per 100,000 persons (95% CI, 296 to 897) for symptomatic Covid-19. The estimated vaccine effectiveness against symptomatic Covid-19 was 18% (95% CI, -2 to 34) at 14 to 27 days after the first dose and 48% (95% CI, 29 to 63) at 7 to 21 days after the second dose. We observed a trend toward higher vaccine effectiveness in the youngest age group (5 or 6 years of age) than in the oldest age group (10 or 11 years of age).ConclusionsOur findings suggest that as omicron was becoming the dominant variant, two doses of the BNT162b2 messenger RNA vaccine provided moderate protection against documented SARS-CoV-2 infection and symptomatic Covid-19 in children 5 to 11 years of age. (Funded by the European Union through the VERDI project and others.).Copyright © 2022 Massachusetts Medical Society.

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