The overall incidence of myopericarditis from 22 studies (405,272,721 vaccine doses) was 33·3 cases (95% CI 15·3–72·6) per million vaccine doses, and did not differ significantly between people who received COVID-19 vaccines and those who received non-COVID-19 vaccines.

Compared with COVID-19 vaccination, the incidence of myopericarditis was significantly higher following smallpox vaccinations but was not significantly different after influenza vaccinations or in studies reporting on various other non-smallpox vaccinations.

Among people who received COVID-19 vaccines, the incidence of myopericarditis was significantly higher in males (vs females), in people younger than 30 years (vs 30 years or older), after receiving an mRNA vaccine (vs non-mRNA vaccine), and after a second dose of vaccine (vs a first or third dose).

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