Myocarditis following vaccination with Pfizer-BioNTech BNT162b2 against coronavirus infection (COVID-19)

Postvaccination myocarditis was reported as early as 1957 in association with smallpox vaccination. Following Emergency Use Authorization of the Pfizer-BioNTech BNT162b2 vaccine by the FDA on December 11, 2020, approval was granted in Israel on December 20, 2020. A national vaccination campaign for novel coronavirus infection (COVID-19) using the Pfizer vaccine ensued in Israel. The vaccination campaign was based on a 2-dose regimen administered with a 21-day interval, and later a third (booster) vaccine was added. A unique nationwide active surveillance program with hospital reports of diagnoses of myocarditis and verification of vaccinations. Based on comparisons with historical (pre-COVID-19) incidence of myocarditis, observed-to-expected ratios were calculated. The results clearly demonstrated an association between vaccination and myocarditis, mainly in young males and mainly in the first week after the second vaccine. These studies are the only nationwide active surveillance studies performed to date and provide the most accurate estimates of myocarditis occurrence after the Pfizer-BioNTech BNT162b2 mRNA-based vaccination.