During a contentious hearing on Thursday, US health secretary Robert F. Kennedy Jr. appeared before the Senate finance committee. Lawmakers interrogated him about his vaccine skepticism, assertions about a politicized scientific community, and the ongoing issues at the Centers for Disease Control and Prevention (CDC).

The hearing, which lasted over three hours and was supposed to address the Trump administration’s healthcare strategies, saw Kennedy defend his tenure at the Department of Health and Human Services (HHS). He claimed that his focus would remain on unbiased, politically neutral, and evidence-based science in the public interest.

Senate Democrats, led by ranking member Ron Wyden from Oregon, opened the session by calling for Kennedy’s resignation. Wyden criticized Kennedy’s approach, saying it threatens public health and urged him to be truthful. “Robert Kennedy’s main agenda is to limit vaccine availability to Americans,” Wyden stated.

Kennedy recently dismissed CDC director Susan Monarez shortly after her confirmation. Monarez is now pursuing a legal challenge against her termination.

Following Monarez’s departure, several senior CDC officials resigned, citing dissatisfaction with Kennedy’s vaccine policies and leadership style.

When questioned about Monarez’s firing, Kennedy claimed she admitted to not being “trustworthy.” However, Senator Elizabeth Warren criticized this reasoning, highlighting Kennedy’s prior description of Monarez as “unimpeachable.”

Kennedy said that Monarez was “lying” when she said her firing was a result of refusing to sign off on the secretary’s new vaccine policies.

“You had full confidence in her and you had full confidence in her scientific credentials, and in a month she became a liar?” Warren asked.

Kennedy also justified wider firings at the CDC , calling them “absolutely necessary”.

“We are the sickest country in the world,” he said. “That’s why we need the fire people at CDC. They did not do their job. This was their job to keep us healthy.”

In June, Kennedy fired all 17 members of the CDC’s vaccine advisory committee – a move that defied a promise he made during his confirmation hearing to Republican senator Bill Cassidy, a physician who chairs the Senate health committee. Many of Kennedy’s replacements for the advisory panel have a history of vaccine skepticism.

When asked about the changes to the advisory committee, and how that will change the vaccine recommendations and scheduling, Kennedy said he didn’t anticipate changes to the MMR (measles, mumps and rubella) vaccine.

In an exchange with Kennedy, Cassidy noted the possible conflict of interest with some of the panel’s new members who are involved in ongoing litigation with vaccine manufacturers.

Cassidy cast a critical vote to confirm Kennedy earlier this year. He had previously expressed a number of concerns about the health secretary’s historic comments that undermined vaccine efficacy. He has since been critical of a number of Kennedy’s policies, including his decision to cut half a billion dollars worth of mRNA vaccine funding – calling the move “unfortunate”.

Last month, the Food and Drug Administration (FDA) approved the new batch of Covid-19 vaccines, but placed restrictions on who would be able to access them. The agency has authorized shots for people 65 and older, who are known to be more at risk from serious illnesses from Covid infections. Younger people will only be eligible if they have an underlying medical condition that makes them vulnerable. Infectious disease experts say that this policy could prove extremely dangerous, particularly for young children.

On Tuesday, Kennedy defended HHS’s handling of the measles outbreak that affected several states in an opinion piece. While the secretary branded his agency’s response as effective, public health experts said Kennedy’s own messaging around vaccines was muddied and confusing.

Cassidy concluded his questioning at the hearing by telling Kennedy that his policies were “effectively denying people the vaccine”, sharing an email from a doctor friend who expressed confusion about Covid inoculation eligibility given the FDA’s new recommendation policies.

Kennedy snapped back: “You’re wrong.”

The Republican senator John Barrasso, of Wyoming, also a doctor, expressed similar concerns about Kennedy’s policies. “In your confirmation hearing you promised to uphold the highest standard for vaccines,” Barrasso said. “Since then, I’ve grown deeply concerned.”

Multiple Democrats on the committee had heated exchanges with the health secretary. Many of them pointed out the inconsistency in Kennedy’s recent support for the president’s “Operation Warp Speed” and his disparagement of the Covid-19 shot. He has previously called it the “deadliest” vaccine ever manufactured.

“Trump has said the vaccine works, and has saved millions of lives. Your own process, on the other hand, has not been transparent,” said the Democratic senator Maggie Hassan, of New Hampshire. “You repeatedly choose to ignore data because it doesn’t match your preconceived notions and lies.”