Robert F. Kennedy Jr.’s nomination to be the nation’s top health official is uncertain after a key Republican joined Democrats to raise persistent concerns over the nominee’s deep skepticism of routine childhood vaccinations that prevent deadly diseases.

The exchanges show how RFK Jr. has failed to update his views on important health issues, even when presented with new science.

Kennedy has downplayed his history of advocating against vaccines since he was nominated to lead the Department of Health and Human Services.

Robert F. Kennedy Jr. appeared before the Senate Committee on Finance on Wednesday as he seeks confirmation to lead the Department of Health and Human Services. Kennedy, a former Democrat, addressed criticism that he is anti-vaccine,

RFK Jr. claimed he is not “anti-vaccine” and appeared unfamiliar with key aspects of healthcare insurance programs in his confirmation hearing.

Robert F. Kennedy Jr. faced intense scrutiny Wednesday on Capitol Hill as he sought confirmation for the role of Health and Human Services secretary.

Robert F. Kennedy Jr., nominee for the U.S. Department of Health and Human Services, faces scrutiny for his past vaccine stance and other controversial remarks. During Senate hearings, both proponents and opponents highlighted Kennedy's history of vaccine misinformation.

Over many years, Kennedy has been clear about his beliefs on vaccines in dozens of interviews, podcasts and social media posts.

Kyra Kennedy, 29, is the youngest daughter of health secretary nominee Robert F. Kennedy Jr.

Kennedy faced questions from the Senate Finance Committee, including from MA Sen. Warren, weighing whether he is fit to be Health Secretary.

Robert F. Kennedy Jr. has said vaccines are not safe. His support for abortion access has made conservatives uncomfortable.

RFK Jr.’s long record of questioning the safety of childhood vaccinations persisted as a flash point for him during a confirmation hearing where a key Republican quickly raised concerns about his views.