Former Centers for Disease Control and Prevention (CDC) Director Susan Monarez will be in the spotlight Wednesday at a high-profile Senate hearing, as Sen. Bill Cassidy (R-La.) appears to try to drive a wedge between Health Secretary Robert F. Kennedy Jr. and President Trump.

Cassidy has shown growing frustration with Kennedy and the chaos he is causing across the federal health department. Wednesday’s hearing will spotlight some of Kennedy’s most high-profile critics within the public health system.

Monarez is set to testify in Cassidy’s Health Committee alongside Deborah Houry, the CDC’s former chief medical officer who resigned in protest after Monarez was fired.

In a matter of weeks earlier this year, Monarez was endorsed by Kennedy, confirmed by the GOP-controlled Senate, and then subsequently ousted, she says, because she would not go along with Kennedy’s vaccine agenda.

According to testimony obtained by The Hill, Monarez will say she was fired for “holding the line on scientific integrity” and refusing to bow under pressure from Kennedy to preapprove recommendations by the agency’s independent vaccine advisory committee Kennedy stocked with vaccine skeptics.

Wednesday’s hearing marks the latest high-stakes moment for Cassidy, a physician-turned-politician from deep-red Louisiana.  

Cassidy agonized about supporting Kennedy’s confirmation due to his record of anti-vaccine views, but ultimately cast the deciding vote for the nomination to advance out of committee after receiving assurances about vaccine policy.

The two-term senator has been on politically shaky ground since he voted to convict President Trump in his impeachment trial over the Jan. 6 riot. Trump has so far remained neutral in Cassidy’s reelection campaign, but the senator’s decision to call Monarez to testify about her departure could rankle the president.

GOP senators deferred to Cassidy’s expertise and prerogative as committee chair, though some questioned whether such a hearing was necessary.

“I’m not the biggest fan of retrospective hearings. I’m not sure how much we’ll learn,” Sen. Josh Hawley (R-Mo.) told The Hill. “[Monarez] is a political appointee. She serves at the pleasure of the president. My understanding is president asked her to resign. She said no. He fired her.” 

Sen. Rand Paul (R-Ky.), who has tangled with Cassidy over vaccines in past hearings, said he thought Monarez’s claim about being asked to rubber-stamp anti-vaccine recommendations was “made up.” 

“I think that she didn’t go to the position with good faith. She did not go to the position willing to support the science,” Paul said. “I think it was right of her to leave the administration, and frankly, I’m glad she’s gone.” 

Until recently, Cassidy has proceeded cautiously. He has called for oversight without directly criticizing Kennedy.

In February, he praised Kennedy for a tepid endorsement of the measles vaccine amid an outbreak in West Texas.  

When Kennedy fired all 17 members of the CDC’s vaccine panel, Cassidy responded on social media but did not openly question Kennedy. 

“Of course, now the fear is that the ACIP will be filled up with people who know nothing about vaccines except suspicion,” he wrote at the time.

But when Kennedy testified before the Senate Finance Committee following his ouster of Monarez, Cassidy grilled the secretary on his vaccine skepticism, arguing his actions flew in the face of one of Trump’s biggest achievements. 

“Effectively, we’re denying people vaccines,” Cassidy told Kennedy in a contentious exchange. 

“You’re wrong,” Kennedy shot back. 

It was the strongest pushback and most contentious public exchange between the two since Kennedy’s term began.  

During the hearing and repeatedly after, Cassidy has called for Trump to receive a Nobel Peace Prize for work developing Operation Warp Speed for the COVID-19 vaccines. 

Cassidy repeated that call in an op-ed published in the conservative National Review magazine Tuesday with Sen. John Barrasso (R-Wyo.), the second-ranked Republican in the Senate and a fellow former physician. 

“Operation Warp Speed was more than a medical achievement. It was a triumph of American greatness and leadership. It was the type of success that reminds us why the President of the United States is the leader of the free world,” the senators wrote. “The Nobel Peace Prize has been given for much less. The next one should go to President Trump.”  

In another nod to Trump, Cassidy framed Wednesday’s hearing with Monarez as “delivering President Trump’s mission to restore radical transparency” at the CDC. 

Last week, Cassidy urged Kennedy to join him in endorsing a childhood vaccine for whooping cough.

“I want to work together to stop pertussis. Your strong public support for this vaccine will save lives,” Cassidy wrote in an open letter, citing Trump’s recent comments supporting vaccines. 

“They just pure and simple work. They’re not controversial at all,” Trump said in the Oval Office on Sept. 5. “And I think those vaccines should be used, otherwise some people are going to catch it and they endanger other people. And when you don’t have controversy at all, I think people should take it.”