Studies have found no evidence of increased risk of cardiac arrest after COVID vaccination. Elon Musk claimed on Twitter that COVID vaccines may be the cause for basketball player Bronny James’ cardiac arrest and other young athletes’ heart issues. There is no evidence that James’ cardiac arrest was linked to COVID vaccination.

Pfizer and Moderna's COVID vaccines have been linked to extremely rare cases of myocarditis (inflammation of the heart muscle), but myocarditis is more common and serious after COVID infection than after getting the COVID vaccine.