Health and Human Services Secretary Robert F. Kennedy Jr. faced a grilling before the Senate Finance Committee on Thursday amid turmoil at the Centers for Disease Control and Prevention (CDC) and his controversial views on vaccines.

Kennedy clashed repeatedly with Democrat and Republican senators alike, many of whom questioned Kennedy’s handling of vaccine policy.

He spent about three hours defending himself and his actions a week after the ousting of Susan Monarez as CDC director and major vaccine changes, including limiting access to the COVID-19 vaccine.

During the hearing, Kennedy was far more combative than in previous appearances on Capitol Hill, notably getting into heated arguments with GOP senators and accusing some Democrats of “making things up” and speaking “gibberish.”

Here are four key takeaways:

Kennedy defends CDC shake-ups, firing of Monarez

Kennedy defended the recent shake-ups at the CDC, including the ousting of newly installed CDC director Monarez and the four officials who resigned shortly after in protest.

Monarez, who was in the job for only a month, was pushed out after she declined to fire top officials and pledge to support Kennedy’s vaccine policy changes in a meeting with the secretary early last week, a source familiar with her conversations with the secretary previously told ABC News.

In an op-ed published in The Wall Street Journal on Thursday morning, Monarez repeated the claim, stating she was fired partly because she wouldn’t prematurely sign off on vaccine recommendations from the CDC’s vaccine advisory committee.

Early on, Senate Finance Committee ranking member Sen. Ron Wyden, a Democrat from Oregon, asked if Monarez’s claims were true, which Kennedy denied.

“Did you, in fact, do what Director Monarez has said you did, which is tell her, ‘Just go along with vaccine recommendations, even if you didn’t think such recommendations aligned with scientific evidence?'” Wyden asked.

“No, I did not,” Kennedy replied.

“So, she’s lying today to the American people in The Wall Street Journal,” Wyden said.

“Yes, sir.”

In a fiery exchange later on with Sen. Elizabeth Warren, a Democrat from Massachusetts, she noted that Kennedy had described Monarez an “unimpeachable” after she was confirmed but was currently saying she is lying.

“I told her that she had to resign because I asked her, ‘Are you a trustworthy person?’ And she said, ‘No,'” Kennedy replied. “If you had an employee who told you they weren’t trustworthy, would you ask them to resign, Senator?”

Kennedy reiterated the statement when asked by Sen. Bernie Sanders, an independent from Vermont, about the exchange with Monarez.

“Are you telling us that the former head of CDC, you asked her, ‘Are you a trustworthy person?’ And she said, ‘No, I am not a trustworthy person,'” Sanders asked.

‘”She didn’t say, ‘No, I’m not a trustworthy person.’ She said, ‘No,'” Kennedy replied.

In a statement from her attorneys, Monarez pushed back on Kennedy’s narrative of the events last week that led to her firing. Her lawyers call it “false” and “patently ridiculous.”

“Dr. Monarez stands by what she said in her op-ed in The Wall Street Journal, would repeat it all under oath and continues to support the vision she outlined at her confirmation hearing that science will control her decisions,” her lawyers, Mark Zaid and Abbe Lowell, said in a statement.

Later, Sanders said he would bring Monarez to Capitol Hill to testify.

“I look forward to her coming before the HELP Committee, maybe this committee as well,” Sanders said, referencing the Senate Committee on Health, Education, Labor and Pensions.

Kennedy also defended the recent shake-ups at CDC saying they were “absolutely necessary adjustments to restore the agency to its role as the world’s gold standard public health agency with a central mission of protecting Americans from infectious disease.”

He claimed,”new blood” is needed at CDC and that it is “imperative that we remove officials with conflicts of interest and catastrophically bad judgment and political agendas.”

Doctors and other public health experts have pointed out that Kennedy has filled open CDC positions with people who hold vaccine skeptical views and have earned income testifying against vaccine makers.

Cassidy, some other Republicans join Democrats in challenging Kennedy on vaccines

Tough questioning from Democrats has been a constant in Kennedy’s previous public hearings with senators, but Thursday saw several Republicans challenge the secretary over vaccines, as well.

Sen. Bill Cassidy, the Louisiana Republican and physician who struggled with his support for Kennedy but ultimately helped seal his confirmation to lead America’s public health agencies, questioned Kennedy’s support for Operation Warp Speed, the major Trump-era effort that led to the rapid launch of mRNA COVID vaccines.

Kennedy said the president deserves a Nobel Prize for Operation Warp Speed, but Cassidy pointed out several ways Kennedy has worked to undermine mRNA vaccines, including Kennedy’s cancelling $500 million in federally-funded mRNA vaccine funding and changing vaccine policy to apply to a narrower group of Americans.

On the Food and Drug Administration’s (FDA) recent changes to COVID vaccine access, Cassidy said, “I would say, effectively, we’re denying people vaccines.”

Two other Republicans on the committee, Sens. John Barrasso of Wyoming and Thom Tillis of North Carolina, expressed concern over Kennedy’s handling of vaccines and the CDC.

Barrasso, also a physician, said he had “grown deeply concerned” since Kennedy took over HHS.

“Over the last 50 years, vaccines are estimated to have saved 154 million lives worldwide,” he said, citing data from the World Health Organization. “I support vaccines. I’m a doctor. Vaccines work.”

Tillis suggested that Kennedy had backtracked on promises he had made to the committee.

“You said you’re going to empower the scientists at HHS to do their job. I’d just like to see evidence where you’ve done that,” Tillis said.

He also questioned the firing of CDC director Monarez after just a few weeks on the job.

“I don’t see how you go over four weeks from, ‘public health expert with unimpeachable scientific credentials, a long-time champion of MAHA values, caring and compassionate and a brilliant microbiologist,’ and four weeks later, fire her,” said Tillis, quoting things Kennedy previously said about Monarez.

Cassidy has tasked the committee he chairs, the Senate HELP Committee, to perform “oversight” of Monarez’s ousting, he wrote on X last week, and he indicated after Thursday’s hearing that he was still pursuing that.”

Kennedy has also faced scrutiny from other Republicans, including at the highest level. Senate Majority Leader John Thune said Kennedy had to “take responsibility” for firing Monarez just four weeks after the Senate confirmed her, while Republican Sen. Susan Collins of Maine said she didn’t see any “justification” for the termination.

Republican Sen. John Kennedy, Cassidy’s counterpart in Louisiana, called the CDC a “multiple vehicle pileup.”

Senators press for clarity on COVID vaccine access

Since the FDA changed COVID vaccine approvals last week to apply to older, higher risk Americans, there has been increasing confusion over who can get a vaccine, driven by differing rules depending on which state people live in or even which pharmacy they frequent.

Despite the reality playing out on the ground, Kennedy maintained on Thursday that “everybody can get access” to the shots — but in a tense back-and-forth with Warren, eventually acknowledged some of the caveats that have interrupted peoples’ attempts to get their shots.

“Most Americans” would be able to get the shot, and it depends on the state, Kennedy said.

“It depends on the state, but they can still get it,” Kennedy said. He argued that there was not enough data to show that COVID vaccines were necessary for healthy, young people.

Warren threw Kennedy’s own words at him: “You promised that you would not take away vaccines from anyone who wanted them,” she said, quoting Kennedy from November.

“It takes it away if you can’t get it from your pharmacy, it takes it away if you have to pay $200,” Warren added.

According to pharmacists, insurance groups and trade organizations, the FDA approval change will make it more difficult for younger, otherwise healthy people to get a COVID-19 vaccine ahead of the winter respiratory virus season, as it will involve a trip to the doctor instead of walking into a pharmacy, and insurance coverage is, for now, unclear.

For at least the next few weeks until a CDC committee weighs in with more detail, and as the policy shifts are absorbed, the confusion may also impact access for older, higher-risk people.

This reality is playing out at CVS pharmacies nationwide, which is the largest pharmacy chain in the country.

In 34 states, CVS will continue to offer COVID vaccines for those who fall under the new FDA authorizations.

But in another 13 states, people will need a prescription to get a COVID shot, even if they are older or high risk. Additionally, in three states, New Mexico, Nevada and Massachusetts, CVS is holding off on giving COVID shots, company spokesperson Amy Thibault said, citing “the current regulatory environment.”

Walgreens, another large pharmacy chain, said it would give shots where it was legally able to do so, but didn’t specify which states would have which rules.

Kennedy also refused to say during the hearing that over one million Americans died from COVID-19 — as recorded by the CDC — and that COVID-19 vaccines saved millions of lives, as determined by analyses.

Kennedy appears combative during testimony

The three-hour hearing quickly became combative as Kennedy defended his time as HHS secretary amid a flurry of questions on his staffing shakeups, vaccine changes and other issues.

A particularly tense exchange with Democratic Sen. Michael Bennet from Colorado began with Bennet having to repeatedly call to get Kennedy’s attention, as the secretary appeared to be looking at something else. The two went on to yell over one another over vaccines, with Kennedy accusing Bennet of evading a question and the senator retorting, “I’m asking the questions!”

He later accused Democratic Sen. Maggie Hassan of New Hampshire of “making stuff up to scare people” when she pressed him on why the change in vaccine recommendations were done “behind closed doors.”

Kennedy said Democratic Sen. Ben Ray Lujan from New Mexico was speaking “gibberish” and said he was “not understanding how the world works” when Lujan asked if he would share the protocols used for a study investigating autism.

Kennedy also took aim at Warren and appeared to suggest she was in the pocket of the pharmaceutical industry. Warren has received money from pharmaceutical companies in the past.

As the hearing came to a close, Kennedy was asked if he would like to make any other statements. “I think I’ll have mercy on everyone here and let us adjourn,” he responded.