Post-EUA safety surveillance reports received by FDA and CDC identified serious risks
for myocarditis and pericarditis following administration of COMIRNATY. Reporting rates
for medical chart-confirmed myocarditis/pericarditis in VAERS have been higher among
males under 40 years of age than among females and older males and have been
highest in males 12-17 years of age (65 cases per million doses administered as per
CDC communication on August 20, 2021), particularly following the second dose, and
onset of symptoms within 7 days following vaccination. Although some cases of vaccineassociated myocarditis/pericarditis required intensive care support, available data from
short-term follow up suggest that most individuals have had resolution of symptoms with
conservative management. Information is not yet available about potential long-term
sequelae and outcomes in affected individuals. A mechanism of action by which the
vaccine could cause myocarditis and pericarditis has not been established.