U.S. Secretary of Health and Human Services Robert F. Kennedy Jr. found himself in the hot seat with both Republicans and Democrats about his vaccine policies Thursday as he appeared before a heated three-hour Senate committee hearing.

A number of Senate Republicans didn't hold back when asking Kennedy pointed questions about his efforts to limit access to vaccines.

Wyoming Sen. John Barrasso, also a doctor and the No. 2 Senate Republican, said he had grown “deeply concerned” that some vaccines could be in jeopardy after Kennedy had cut research funding and fired the CDC director.

"If we're going to make America healthy again, we can't allow public health to be undermined," Barrasso said. “Americans don’t know who to rely on."

Barrasso grilled Kennedy over his guidance on childhood vaccines and said he's worried trust in vaccines could be in jeopardy under Kennedy’s leadership.

Kennedy shot back that Americans have lost faith in the CDC and pledged to make health recommendations “clear, evidence-based and trustworthy for the first time in history."

Senator Bill Cassidy of Louisiana, also a medical doctor, tried to strike a balance between his support for President Donald Trump and his medical ideals.

He praised Trump’s handing of COVID while suggesting Kennedy is making it more difficult for Americans to receive the vaccine.

Early in his line of questioning, Cassidy asked Kennedy whether he agrees that Trump deserves the Nobel Prize for Operation Warp Speed, the initiative that produced and delivered COVID-19 vaccines.

Kennedy responded that he did.

“It surprises me that you think so highly of Operation Warp Speed when as an attorney, you attempted to restrict access to the COVID vaccine," Cassidy shot back.

North Carolina Sen. Thom Tillis read off a list of questions for Kennedy that he said he wanted answered after the hearing, including where the health secretary stands on the COVID-19 vaccine.