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.

Spasmodic dysphonia (SD), sometimes referred to as laryngeal dystonia, is a rare neurological condition impacting the voice and speech that impacts approximately 50,000 people in North America. For people with SD, muscles spasms in the larynx (also known as the voice box) cause the voice to sound tight, strangled or strained.