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.

Kennedy has repeatedly questioned the efficacy and even safety of vaccines touted by most doctors as medical miracles responsible for saving tens of million lives globally.

In one of the most tense exchanges in a heated confirmation hearing, Senator Angela Alsobrooks called out past comments RFK Jr. made suggesting a different vaccine schedule for Black people.