US officials reviewing possibility Moderna vaccine is linked to higher risk of uncommon side effect than previously thought

Moderna’s coronavirus vaccine for adolescents has yet to be authorized by federal health officials in part because they are investigating emerging reports that the shots may be associated with a higher risk of a heart condition in younger adults than previously believed, according to two people familiar with the review who emphasized the side effect still probably remains very uncommon. The investigation, which involves the Food and Drug Administration and the Centers for Disease Control and Prevention, is focusing on Canadian data that suggests the Moderna vaccine may carry a higher risk of myocarditis for young people than the Pfizer-BioNTech vaccine, especially for males below the age of 30 or so.