Kennedy refused to flatly reject a long-discredited theory that vaccines cause autism, despite years of studies and research that have found they do not.

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.

Sanders, the senior minority party member on the committee, pressed Kennedy to concede that health care was a human right, as his father, Robert F. Kennedy, and his uncles, John F. Kennedy and Edward Kennedy, had done. Kennedy again did not give a definitive answer.