Cryptic late‐onset myocarditis after coronavirus vaccination

Abstract

As we enter a new era of mRNA‐based therapeutics, evidence on genetic or environmental factors that might predispose to unknown off‐target side effects, gains in importance. Among these factors, exercise appears likely to have influenced otherwise cryptic cases of early‐onset postvaccination myocarditis. And the existence of a distinct late‐onset myocarditis is now being recognized. Here, three case‐history reports suggest crypticity (the author's own case), unless provoked by a preexisting cardiac morbidity (one case), or by immune checkpoint blockade to enhance anticancer autoimmunity (several cases). These reports are supported by noninvasive fluorodeoxyglucose‐based cardiac scan comparisons of multiple vaccinated and unvaccinated subjects. In pre‐pandemic decades, applications for funds by the leading innovator in mRNA‐based therapeutics seldom gained peer‐review approval. Thus, at the start of the pandemic, the meager data on such side effects could justify only emergency approval. We must do better.