WASHINGTON (AP) — Health Secretary Robert F. Kennedy Jr. is vowing to “fix” the federal program for compensating Americans injured by vaccines, opening the door to sweeping changes for a system long targeted by anti-vaccine activists.

Health experts and lawyers say updates are needed to help clear a backlog of cases in the Vaccine Injury Compensation Program, created by Congress in 1986 as a no-fault payment system for presumed vaccine injuries.

But they also worry Kennedy’s changes will reflect his history as a leader in the anti-vaccine movement, which has alternately called for abolishing the program or expanding it to cover unproven injuries and illnesses that aren’t connected to vaccines.

Kennedy and other critics believe the program is “too miserly in what it considers to be a vaccine injury,” said Jason Schwartz, a public health expert at Yale University. “That’s created great concern that he could expand what’s included.”

Anti-vaccine groups have long suggested a link between vaccines and autism, despite scientific consensus that childhood vaccines don’t cause the condition. Adding autism to the list of injuries covered by the plan “would dramatically increase the number of compensable cases, potentially bankrupting it,” Schwartz said.