Results:

In >42 million individuals receiving ≥1 dose of vaccine, >21 million people received 3 doses, and 5,934,153 had SARS-CoV-2 infection before or after vaccination. Myocarditis occurred in 2,861 (0.007%) people, with 617 events 1-28 days after vaccination. Risk of myocarditis was increased in the 1-28 days after a first dose of ChAdOx1/Oxford-AstraZeneca vaccine (incidence rate ratio, 1.33; [95% CI, 1.09–1.62]) and a first, second, and booster dose of BNT162b2/BioNTech-Pfizer vaccine (1.52 [95% CI, 1.24–1.85]; 1.57 [95% CI, 1.28–1.92], and 1.72 [95% CI, 1.33–2.22], respectively) but was lower than the risks after a positive SARS-CoV-2 test before or after vaccination (11.14 [95% CI, 8.64–14.36] and 5.97 [95% CI, 4.54–7.87], respectively). The risk of myocarditis was higher 1-28 days after a second dose of mRNA-1273/Moderna–National Institute of Allergy and Infectious Diseases (NIAID) vaccine (11.76 [95% CI, 7.25–19.08]) and persisted after a booster dose (2.64 [95% CI, 1.25–5.58]). Associations were stronger in men <40 years old for all vaccines. Importantly, in men <40 years old, the number of excess myocarditis events per million people was higher after a second dose of mRNA-1273/Moderna-NIAID vaccine than after a positive SARS-CoV-2 test (97 [95% CI, 91–99] vs. 16 [95% CI, 12–18]). In women <40 years old, the number of excess events per million was similar after a second dose of mRNA-1273/Moderna-NIAID vaccine and a positive test (7 [95% CI, 1–9] vs. 8 [95% CI, 6–8]).