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.

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.

Sen. Elizabeth Warren discussed her viral back-and-forth with RFK Jr. on Thursday during an interview on "The View," saying the U.S. could be left with "no vaccines."