From December 20, 2020 to May 31, 2021, they found 283 cases of which 142 occurred after receiving the BNT162b2 vaccine. The overall risk difference between the first and second doses was 1.76 per 100,000 people (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 people; 95% CI, 8.11 to 19.46). Compared with the expected incidence based on historical data, the standardized incidence rate was 5.34 (95% CI, 4.48 to 6.40) and was higher after the second dose in male recipients among ages 16 and 19 years (13.60; 95% CI, 9.30 to 19.20). The incidence of myocarditis was slightly increased after receiving the BNT162b2 vaccine in young men who received it. The clinical presentation of myocarditis after vaccination was generally mild.