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.

Robert F. Kennedy Jr., President Donald Trump’s nominee to head the U.S. Department of Health and Human Services, faced grilling from Democrats and at least one Republican on day two of his Senate confirmation hearing.

As Robert F. Kennedy Jr. faced skeptical senators Thursday in the second day of his confirmation hearing to lead the department of Health and Human Services, Sen. Bill Cassidy confronted Kennedy about vaccines.

Robert F. Kennedy's nomination will put Republican lawmakers' loyalty to the test, as the former Democrat holds a range of unorthodox positions that could alienate both conservatives and liberals.

RFK Jr.'s confirmation hearings continue today as he appears before a second Senate committee. Follow STAT's live updates.

Senator Bill Cassidy, a physician and key G.O.P. vote, joined Democrats in aggressively questioning Robert F. Kennedy Jr., President Trump’s pick for health secretary. He did not say how he would vote.

Vaccination bills are popping up in more than 15 states as lawmakers aim to potentially resurrect or create new religious exemptions from immunization mandates, establish state-level vaccine injury databases or dictate what providers must tell patients about the shots.

Robert F. Kennedy Jr. transferred ownership of the trademark application in December and its abbreviation — MAHA — to an LLC managed by Del Bigtree.

That drew quick pushback from Democratic Sen. Ron Wyden of Oregon — and ensuing back and forth between him and Kennedy. Wyden pointed out the health secretary nominee has previously claimed there's “no safe” vaccine. Wyden also quoted from Kennedy's books, which say that parents have been “misled” on the measles vaccine.

RFK Jr.'s "Make America Healthy Again" trademark, now managed by anti-vaccine activist Del Bigtree, is fueling controversy amid his HHS Senate confirmation hearings with concerns over the potential commercialization of vaccines.

The Texas legislature is debating bills that advocates say could give individuals more choice in whether they vaccinate themselves and their children.

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.