Increased cases of myocarditis and pericarditis have been reported in the United States after mRNA COVID-19 vaccination (Pfizer-BioNTech and Moderna) since April 2021, particularly in adolescents and young adults. These rates for ages 16-24 following a second dose are above what is expected. Myocarditis or pericarditis has now been verified in 226 people ages 30 and younger who have received an mRNA COVID-19 vaccine and Federal Health Officials are investigating reports of approximately 250 more cases. Read more.