• Dror Mevorach, Emilia Anis, Noa Cedar, Michal Bromberg, Eric J Haas, Eyal Nadir, Sharon Olsha-Castell, Dana Arad, Tal Hasin, Nir Levi, Rabea Asleh, Offer Amir, Karen Meir, Dotan Cohen, Rita Dichtiar, Deborah Novick, Yael Hershkovitz, Ron Dagan, Iris Leitersdorf, Ronen Ben-Ami, Ian Miskin, Walid Saliba, Khitam Muhsen, Yehezkel Levi, Manfred S Green, Lital Keinan-Boker, and Sharon Alroy-Preis.
• From the Department of Internal Medicine B, Division of Immunology-Rheumatology, and Wohl Institute for Translational Medicine (D.M.) and the Departments of Cardiology (R.A., O.A.), Pathology (K. Meir), and Radiology (D.C.), Hadassah Medical Center, Braun School of Public Health (E.A.), Jesselson Integrated Heart Center, Shaare Zedek Medical Center (T.H., N.L.), and the Department of Family Medicine (I.M.), Faculty of Medicine, Hebrew University of Jerusalem, the Divisions of Epidemiology (E.A., N.C., E.J.H., E.N.), Patient Safety (S.O.-C., D.A.), and Medicine (I.L.), Israeli Ministry of Health (M.B., R. Dichtiar, D.N., Y.H., Y.L., L.K.-B., S.A.-P.), and Clalit Health Services (E.N., I.M.), Jerusalem, Israel Center for Disease Control, and Azrieli Faculty of Medicine, Bar-Ilan University (O.A.), Ramat Gan, the Department of Epidemiology and Preventive Medicine, School of Public Health (M.B., K. Muhsen), and Tel Aviv Sourasky Medical Center (R.B.-A.), Tel Aviv University, Tel Aviv, Ben Gurion University of the Negev, Beer Sheva (E.J.H., R. Dagan), and the Department of Community Medicine and Epidemiology, Lady Davis Carmel Medical Center, Technion-Israel Institute of Technology (W.S.), and the School of Public Health, University of Haifa (M.S.G., L.K.-B.), Haifa - all in Israel.
• N. Engl. J. Med. 2021 Dec 2; 385 (23): 214021492140-2149.

BackgroundApproximately 5.1 million Israelis had been fully immunized against coronavirus disease 2019 (Covid-19) after receiving two doses of the BNT162b2 messenger RNA vaccine (Pfizer-BioNTech) by May 31, 2021. After early reports of myocarditis during adverse events monitoring, the Israeli Ministry of Health initiated active surveillance.MethodsWe retrospectively reviewed data obtained from December 20, 2020, to May 31, 2021, regarding all cases of myocarditis and categorized the information using the Brighton Collaboration definition. We analyzed the occurrence of myocarditis by computing the risk difference for the comparison of the incidence after the first and second vaccine doses (21 days apart); by calculating the standardized incidence ratio of the observed-to-expected incidence within 21 days after the first dose and 30 days after the second dose, independent of certainty of diagnosis; and by calculating the rate ratio 30 days after the second dose as compared with unvaccinated persons.ResultsAmong 304 persons with symptoms of myocarditis, 21 had received an alternative diagnosis. Of the remaining 283 cases, 142 occurred after receipt of the BNT162b2 vaccine; of these cases, 136 diagnoses were definitive or probable. The clinical presentation was judged to be mild in 129 recipients (95%); one fulminant case was fatal. The overall risk difference between the first and second doses was 1.76 per 100,000 persons (95% confidence interval [CI], 1.33 to 2.19), with the largest difference among male recipients between the ages of 16 and 19 years (difference, 13.73 per 100,000 persons; 95% CI, 8.11 to 19.46). As compared with the expected incidence based on historical data, the standardized incidence ratio was 5.34 (95% CI, 4.48 to 6.40) and was highest after the second dose in male recipients between the ages of 16 and 19 years (13.60; 95% CI, 9.30 to 19.20). The rate ratio 30 days after the second vaccine dose in fully vaccinated recipients, as compared with unvaccinated persons, was 2.35 (95% CI, 1.10 to 5.02); the rate ratio was again highest in male recipients between the ages of 16 and 19 years (8.96; 95% CI, 4.50 to 17.83), with a ratio of 1 in 6637.ConclusionsThe incidence of myocarditis, although low, increased after the receipt of the BNT162b2 vaccine, particularly after the second dose among young male recipients. The clinical presentation of myocarditis after vaccination was usually mild.Copyright © 2021 Massachusetts Medical Society.

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