The Food and Drug Administration, led by Health Secretary Robert F. Kennedy Jr., has restricted access to Covid-19 vaccines for adults aged 18 to 64, requiring proof of an underlying medical condition before the shots can be administered. The move, announced late 27 August, immediately drew criticism from lawmakers and public-health specialists who warned it could leave millions vulnerable ahead of the winter respiratory-virus season. Representative Kim Schrier, a Washington Democrat and pediatrician, said the policy “jeopardizes access to vaccines that have been proven to save lives.” Vaccine law scholar Richard Hughes predicted a cascade of practical problems for providers and patients, calling the measure the “main conflict” that will now define U.S. immunization policy. The decision lands amid turmoil inside the Centers for Disease Control and Prevention. CDC Director Susan Monarez, who took office in July, is resisting Kennedy’s demand that she resign, according to her attorneys. Four senior CDC officials quit on 27 August in what colleagues described as frustration over the administration’s vaccine stance. The Department of Health and Human Services said Monarez was “no longer” director, a claim her lawyers dispute, deepening uncertainty at the agency charged with implementing the new vaccination rules.