US health officials are investigating reports that Moderna's COVID-19 vaccine may be linked to a higher risk of a rare heart condition in younger adults than previously thought, the Washington Post reported late on Thursday (Aug 19), citing people familiar with the review.
The report quoted a source saying it was too early for the regulators to reach a conclusion, and that additional work was needed before any recommendation was made.
Health regulators in June had added a warning to the literature that accompanies the mRNA vaccines produced by Moderna and Pfizer to flag the rare risk of heart inflammation seen primarily in young males. However, they said the benefit of the shots in preventing COVID-19 continued to outweigh the risks.
There might be a 2.5 times higher incidence of myocarditis in those who get the Moderna vaccine compared with Pfizer's vaccine, the Post quoted a source as saying.
The investigation that is focused on Canadian data suggests that risks of myocarditis might especially be higher for males below the age of 30 or so, according to the report.
Moderna and the US Food and Drug Administration (FDA) did not immediately respond to Reuters' requests for comment.