Very few cases of myocarditis, or heart inflammation, have been observed as a side effect from a COVID-19 vaccine. The Centers for Disease Control says its recent recommendation to lengthen the period between vaccine doses may reduce the already rare side effect.
The cases haven't affected advice from U.S. health authorities that anyone 5 years or older should get fully vaccinated. People who get sick from COVID-19 are actually at a higher risk of contracting myocarditis, and a more severe case, they note.
The CDC estimates the incidence of COVID-19 vaccine-related myocarditis at 0.48 cases per 100,000. An estimated 1-10 cases per 100,000 occur regardless of vaccination status.
A study conducted between December 2020 and August 2021 reported 1,991 cases among 192.4 million vaccinated individuals.
Among cases, "the great majority...were mild and resolved on their own," according to VCU Health, a Virginia medical center.