The evidence is clear: Myocarditis developed rapidly in younger patients, mostly after the second vaccination. Pericarditis affected older patients later, after either the first or second dose.

‘Forty hospitals in Washington, Oregon, Montana, and Los Angeles County, California, that were part of the Providence health care system and used the same electronic medical record (EMR) were included. All patients with documented COVID-19 vaccinations administered inside the system or recorded in state registries at any time through May 25, 2021, were identified. Vaccinated patients who subsequently had emergency department or inpatient encounters with diagnoses of myocarditis, myopericarditis, or pericarditis were ascertained from EMRs’.

‘Among 2 000 287 individuals receiving at least 1 COVID-19 vaccination, 58.9% were women, the median age was 57 years (interquartile range [IQR], 40-70 years), 76.5% received more than 1 dose, 52.6% received the BNT162b2 vaccine (Pfizer/BioNTech), 44.1% received the mRNA-1273 vaccine (Moderna), and 3.1% received the Ad26.COV2.S vaccine (Janssen/Johnson & Johnson).

Twenty individuals had vaccine-related myocarditis (1.0 [95% CI, 0.61-1.54] per 100 000) and 37 had pericarditis (1.8 [95% CI, 1.30-2.55] per 100 000).’

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