Overall risk for myocarditis is higher after a positive SARS-CoV-2 test than after COVID-19 vaccination, according to a study published in Circulation. Julia Hippisley-Cox, MBChB, MD, FRCP, DRCOG, FRCGP, and colleagues estimated the incidence rate ratio (IRR) and excess number of hospital admissions or deaths from myocarditis per million people aged 13 and older for the 1-28 days following adenovirus or mRNA-based vaccine doses or a positive SARS-CoV-2 test. Data were included for nearly 43 million people receiving at least one dose of vaccine, approximately 21 million of whom received three doses; nearly 6 million had SARS-CoV-2 infection before or after vaccination. The researchers found that 2,861 people (0.007%) had myocarditis, with 617 events 1-28 days after vaccination. Elevated myocarditis risk was seen at 1-28 days after a first dose of adenovirus-based vaccine (IRR, 1.33) and a first, second, and booster dose of mRNA-based vaccine (IRRs, 1.52, 1.57, and 1.72, respectively), but was lower than after a positive SARS-CoV-2 test before or after vaccination (IRRs, 11.14 and 5.97, respectively).
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