Editing Openai/6944461c-7f90-8000-8c32-54fe2958dd9a (section)

===== Boldest signal that has actually been studied is myocarditis (inflammation of the heart) — not thousands of events, but a small cluster seen after mRNA COVID-19 vaccines: =====
* A JAMA Cardiology research brief described cases of myocarditis in 23 generally healthy U.S. service members (median age ~25) who developed acute chest pain within about 4 days after vaccination with mRNA vaccines (Pfizer or Moderna). Most occurred after the second dose of the primary series. This was out of millions of doses given in the military population. siicsalud.com<ref>{{cite web|title=siicsalud.com|url=https://www.siicsalud.com/dato/resiic.php/167589|publisher=siicsalud.com|access-date=2025-12-20}}</ref>
* Earlier analyses also noted this finding: myocarditis was observed and reported among military members shortly after mRNA vaccination. JAMA Network<ref>{{cite web|title=JAMA Network|url=https://jamanetwork.com/journals/jamacardiology/fullarticle/2781601|publisher=JAMA Network|access-date=2025-12-20}}</ref>
* These reports are consistent with external civilian studies showing elevated myocarditis risk in young males after mRNA COVID-19 vaccines, including military-age demographics, although these events remain rare in absolute terms. AHA Journals<ref>{{cite web|title=AHA Journals|url=https://www.ahajournals.org/doi/10.1161/CIRCULATIONAHA.121.056135|publisher=AHA Journals|access-date=2025-12-20}}</ref>

Context & interpretation:
Myocarditis in this reporting is not common — it was a signal, not a widespread epidemic — and researchers highlight both the temporal association and the need for careful surveillance, but also that these events are uncommon relative to the massive number of doses administered. siicsalud.com<ref>{{cite web|title=siicsalud.com|url=https://www.siicsalud.com/dato/resiic.php/167589|publisher=siicsalud.com|access-date=2025-12-20}}</ref>