A rare risk for myocarditis (inflammation of the heart muscle) and/or pericarditis (inflammation of the tissue surrounding the heart) has been observed following receipt of mRNA COVID-19 vaccines and Novavax COVID-19 Vaccine. Despite this observation, evaluation demonstrates that the benefits of vaccination clearly outweigh the risks in all age groups.
Among mRNA vaccine recipients, these rare cases of myocarditis or pericarditis have occurred most frequently in adolescent and young adult males within the first week after receiving the second dose of an mRNA COVID-19 vaccine primary series. Myocarditis is even more rare in children younger than age 12 years after COVID-19 vaccination. This risk appears related to age, biological sex, and the short (3- to 4-week) interval between primary series doses. Extending the interval to 8 weeks for some people for whom a vaccination series is recommended may reduce the rare risk of myocarditis following the second dose.
Most patients diagnosed with myocarditis after mRNA COVID-19 vaccination have been hospitalized for short periods, with most completely recovering from their acute symptoms. CDC is assessing long-term outcomes in people with myocarditis after mRNA COVID-19 vaccination.
People receiving COVID-19 vaccines, especially males age 12 through 39, should be counseled about the risk of myocarditis or pericarditis and advised to seek medical attention promptly if they develop chest pain, shortness of breath, or feelings of a fast, fluttering, or pounding heartbeat.
Cases of myocarditis and pericarditis were identified in clinical trials of Novavax COVID-19 Vaccine and have also been reported during post-authorization use outside the United States. These findings suggest that an increased risk for these conditions may be present after receiving Novavax COVID-19 vaccine.
Current recommendations are for a single dose of any FDA-licensed or FDA-authorized updated (2023–2024 Formula) COVID-19 vaccine for most people age 5 years and older, even if the individual is previously unvaccinated. Previously unvaccinated individuals who receive Novavax vaccine are recommended to receive two doses, given three to 8 weeks apart.
CDC’s complete interim clinical considerations for COVID-19 vaccination and myocarditis or pericarditis are available here: www.cdc.gov/vaccines/covid-19/clinical-considerations/interim-considerations-us.html#myocarditis-pericarditis.
CDC also has published additional clinical considerations for the evaluation and care of patients with myocarditis or pericarditis following mRNA vaccination: www.cdc.gov/vaccines/covid-19/clinical-considerations/myocarditis.html.