Sen. Bill Cassidy, the top Republican on the Senate Committee on Health, Education, Labor and Pensions, concluded Thursday's hearing by saying he was "struggling" with the nomination due to Kennedy's vaccine positions. Kennedy notably refused to say vaccines don't cause autism as he faced pointed question from lawmakers.

During his Senate confirmation hearing, Kennedy claimed he is not against vaccination, contrary to decades of public comments.

Robert F. Kennedy Jr. faced about 3.5 hours of questioning on topics including his past comments on vaccines and abortion during the first of his two confirmation hearings.