The U.S. Food and Drug Administration has ordered Pfizer and Moderna to add stronger language on the risk of myocarditis and pericarditis to the labels of their mRNA COVID-19 vaccines, Comirnaty and Spikevax. The decision, announced in a 25 June safety communication and published 3 July, expands earlier warnings and for the first time quantifies the incidence of post-vaccination heart inflammation. According to FDA-backed data covering the 2023–24 vaccine formulation, myocarditis has occurred at a rate of about eight cases per one million recipients aged six months to 64 years. The risk is highest among males aged 12 to 24, with an estimated 27 cases per million doses. The updated labeling also references imaging data showing that some patients continue to exhibit cardiac abnormalities months after diagnosis, although the long-term clinical implications remain uncertain. Pfizer and Moderna must revise Prescribing Information, patient and caregiver fact sheets, and emergency-use documents, and continue ongoing studies tracking long-term outcomes for vaccine-associated myocarditis. The FDA action follows an April directive to the companies and comes amid divergent views inside the U.S. government; the Centers for Disease Control and Prevention has said recently that it sees no increased myocarditis signal in its injury databases since 2022. Both agencies agree the condition is rare and usually less severe than myocarditis linked to COVID-19 infection itself.