A newly released cache of internal Food and Drug Administration memos shows that Dr. Vinay Prasad, the agency’s recently appointed vaccine chief, overruled staff scientists to narrow the authorization of two COVID-19 vaccines made by Novavax and Moderna. FDA reviewers had recommended clearing both shots for everyone aged 12 and older after concluding the benefits outweighed the low risk of side effects. In a five-page override memo dated 2 July, Prasad instead limited the vaccines to seniors and people with underlying health conditions, citing falling hospitalization and death rates and lingering questions about rare cases of myocarditis. The move is the latest in a series of vaccine policy shifts under Health Secretary Robert F. Kennedy Jr., a long-time critic of broad immunization campaigns. Prasad assumed control of the FDA’s vaccine center in May after the departure of longtime director Dr. Peter Marks and has been working with Commissioner Mark Makary on guidelines that would confine future COVID booster approvals to high-risk groups. COVID-19 remains a persistent threat, causing an estimated 32,000 to 51,000 U.S. deaths and more than 250,000 hospitalizations since last autumn, according to the Centers for Disease Control and Prevention. As a condition of authorization, Moderna must conduct further studies on myocarditis, while broader access to both vaccines will depend on additional data and any future FDA review.