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

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

What to know from Robert F. Kennedy, Jr.’s hearings before the Senate Finance Committee on Wednesday and the Senate Health, Education, Labor, and Pensions on Thursday.

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

Robert F. Kennedy Jr. will stand before the Senate Finance Committee on Wednesday and the Senate Health, Education, Labor and Pension Committee Thursday as President Donald Trump's nominee to lead the Department of Health and Human Services.

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If approved, Kennedy will control a $1.7 trillion agency that oversees food and hospital inspections, hundreds of health clinics, vaccine recommendations and health insurance for roughly half the country.

As he seeks to lead the health department, Mr. Kennedy wore a thin tie dotted with feathered creatures to cap a classic suit.

Caroline Kennedy sharply criticized her cousin Robert F. Kennedy Jr. in a pointed open letter to the U.S. Senate, describing him as a “predator” and imploring lawmakers to reject his potential appointment as Secretary of Health and Human Services.

The hearings were packed to capacity with protesters and fans, while the spillover crowd hung out in hallways and overflow rooms.

Robert F. Kennedy, President Trump’s nominee for health secretary, vigorously defended his views on vaccines, and a key senator still has clear doubts.