AMNA NAWAZ: Welcome to the "News Hour."

Health Secretary Robert F. Kennedy Jr. was grilled during a contentious three-hour hearing before the Senate Finance Committee today.

GEOFF BENNETT: Senators pressed Kennedy on his stance toward vaccines, questioning whether his actions have restricted access and undermined trust in longstanding public health data and institutions.

The hearing turned combative at times, with Kennedy clashing directly with several lawmakers.

The confrontation came just a week after his controversial decision to fire the director of the CDC.

Lisa Desjardins leads our coverage now from Capitol Hill.

LISA DESJARDINS: In a small Senate hearing room... SEN. RAPHAEL WARNOCK (D-GA): You are a hazard to the health of the American people.

LISA DESJARDINS: ... high-stakes fireworks.

ROBERT F. KENNEDY JR., U.S. Health and Human Services Secretary: I never said that.

You're making it up.

SEN. TINA SMITH (D-MN): I am not.

ROBERT F. KENNEDY JR.: You're twisting.

Yes, you are.

You are being dishonest right now.

(CROSSTALK) SEN. TINA SMITH: You ... LISA DESJARDINS: As health secretary, Robert F. Kennedy Jr. faced his first hearing since being in the job and since Kennedy upended the Centers for Disease Control, firing his own choice as director and triggering senior resignations.

ROBERT F. KENNEDY JR.: What we're going to do is reorganize CDC, but also we have already righted the ship at NIH and FDA, at CMS.

And we are going to end the chronic disease epidemic.

LISA DESJARDINS: It was perhaps the most combative hearing of Trump's second term so far.

SEN. MARK WARNER (D-VA): You are sitting as secretary of health and human services?

How can you be that ignorant?

ROBERT F. KENNEDY JR.: You're so wrong on your facts.

SEN. MARIA CANTWELL (D-WA): You're interrupting me.

And, sir, you're a charlatan.

That's what you are.

LISA DESJARDINS: Kennedy argued he's remaking a broken agency, particularly lashing out at pandemic recommendations.

ROBERT F. KENNEDY JR.: The people at CDC who oversaw that process, who put masks on our children, who closed our schools are the people who will be leaving.

LISA DESJARDINS: But senators from both parties sharply rejected parts of his premise, saying Kennedy is the one breaking the system, pushing him on his understanding of basic facts.

SEN. MARK WARNER: Do you accept the fact that a million Americans died from COVID?

ROBERT F. KENNEDY JR.: I don't know how many died.

SEN. MARK WARNER: You're the secretary of health and human services.

You don't have any idea how many Americans died from COVID?

ROBERT F. KENNEDY JR.: I don't think anybody knows that.

SEN. MARK WARNER: Do you think the vaccine did anything to prevent additional deaths?

ROBERT F. KENNEDY JR.: Again, I would like to see the data and talk about the data.

LISA DESJARDINS: Kennedy later said it was possible that millions were saved by the vaccine.

But mostly he displayed deep skepticism of vaccines, a belief now having direct consequences around the country.

Some national drugstores limited or blocked access to COVID shots after new federal guidelines came out.

Florida is trying to end vaccine rules for schoolkids.

Three states are forming their own vaccine pact, and many other states are in limbo.

Senators, including Republicans, expressed alarm about the lack of data they see to support Kennedy.

SEN. THOM TILLIS (R-NC): You said you're going to empower the scientists at HHS to do their job.

I'd just like to see evidence where you have done that.

SEN. JOHN BARRASSO (R-WY): I have grown deeply concerned.

The public has seen measles outbreaks, leadership at the National Institute of Health questioning the use of mRNA vaccines.

If we're going to make America healthy again, we can't allow public health to be undermined.

LISA DESJARDINS: Kennedy and senators used the same words, but often spoke confusingly different languages.

ROBERT F. KENNEDY JR.: I'm not anti-vaccine.

Saying I'm anti-vaccine is like saying I'm anti-medicine.

I'm pro-medicine, but I understand some medicines harm people.

Some of them have risks.

LISA DESJARDINS: GOP Senator Bill Cassidy, himself a doctor and the key vote who confirmed Kennedy, raised a specific example of concern from a friend.

SEN. BILL CASSIDY (R-LA): "My wife has stage four lung cancer.

She is one of the people that COVID vaccine actually helps.

Thanks to the current mess at HHS, CVS is unable to get her vaccine."

I would say, effectively, we're denying people vaccine.

LISA DESJARDINS: Democrat Elizabeth Warren pressed on this.

ROBERT F. KENNEDY JR.: I'm not taking away from people, Senator.

Everybody can get access to them.

SEN. ELIZABETH WARREN (D-MA): No, they can't walk into a pharmacy the way that they could last month and get access.

ROBERT F. KENNEDY JR.: It depends on the state.

LISA DESJARDINS: Another flash point, Kennedy's decision to fire the entire board which makes vaccine recommendations known as ACIP.

Kennedy said he made the move to reduce what he calls conflicts of interest.

SEN. RON WYDEN (D-OR): You replaced them with non-experts, vaccine skeptics, and conspiracy theorists.

As a result, this critical advisory panel has lost scientific credibility.

ROBERT F. KENNEDY JR.: What we did is we got rid of the conflicts of interest and we depoliticized and put great scientists on it from a very diverse group.

LISA DESJARDINS: Through it all, the secretary remained defiant and insistent.

SEN. MAGGIE HASSAN (D-NH): You are citing data that you won't produce to the public.

(CROSSTALK) ROBERT F. KENNEDY JR.: You're just making things up.

You're making things up to scare people.

And it's a lie.

LISA DESJARDINS: But multiple Democrats said Kennedy is so dangerous he must resign.

SEN. MICHAEL BENNET (D-CO): I'm asking the questions, Mr. Kennedy, on behalf of parents and schools and teachers all over the United States of America, who deserve so much better than your leadership.

SEN. MIKE CRAPO (R-ID): This hearing is adjourned.

LISA DESJARDINS: The hearing ended with none of the fire quenched, few questions resolved and Kennedy returning to the job.

At the Capitol, for the "PBS News Hour," I'm Lisa Desjardins.