WASHINGTON — Sen. Bill Cassidy, a Republican from Louisiana, questioned Health and Human Services Secretary Robert F. Kennedy on his vaccine skepticism Thursday, suggesting that Kennedy’s stance contradicts one of President Donald Trump’s major achievements.

Cassidy began his questioning at a Senate hearing by asking Kennedy if he believes Trump should be awarded a Nobel Prize for developing the Covid vaccine during his first term, specifically through Operation Warp Speed amidst the pandemic.

Kennedy replied quickly: “Absolutely, senator.”

Cassidy was skeptical.

“But you just told Sen. [Michael] Bennet that the Covid vaccine killed more people than Covid. That was a statement,” Cassidy stated, expressing surprise at Kennedy’s high regard for Operation Warp Speed, while also noting his legal efforts to limit access to the Covid vaccine.

Kennedy refuted the claim that he said the vaccine caused more deaths than Covid and offered to clarify his legal actions against the vaccine. However, Cassidy, pressed for time, remained unconvinced and continued with more questions.

Cassidy referenced opinions from a conservative commentator indicating that HHS’s measures are complicating vaccine access for some Americans and concerns from doctors about the potential legal issues due to a lack of guidance from HHS regarding the vaccine.

“I would say, effectively, we’re denying people vaccine,” Cassidy told Kennedy during his questioning.

This unusual interaction highlights Cassidy’s challenging political balance. As a doctor, he supports vaccines, but he is also campaigning for re-election in Louisiana, a strongly Republican state where he is facing competition from the MAGA faction. Trump has yet to endorse any candidate in the race.

Cassidy’s strategy Thursday was to voice his skepticisms of Kennedy through the language of Trump’s movement: by presenting them as a way to show support for the president and to protect his legacy.

Trump has a complex history on the matter. He took pride in the Covid vaccine rollout during the pandemic. But during his 2024 comeback campaign, Trump also sought to channel anger at the government’s response to Covid within his base — including distrust of public health officials that has translated into some anti-vaccine sentiments.

That led to the partnership between Trump and Kennedy, the scion of a Democratic political dynasty that now eschews his politics, and ultimately, the president’s selection of him as HHS secretary.

Earlier this year, Cassidy, the chair of the Health, Education, Labor and Pensions Committee, openly acknowledged he struggled with Kennedy’s nomination. Cassidy ended up providing critical support for Kennedy after receiving assurances that he wouldn’t sow distrust or damage the availability of vaccines. With Cassidy’s backing, Kennedy advanced to the Senate floor, where he was confirmed 52-48. Sen. Mitch McConnell of Kentucky was the lone Republican to join all Democrats in voting against Kennedy.

Sen. Mark Warner, D-Va., said Kennedy broke his promise to Cassidy and should resign.

“He has completely gone against what he pledged to this committee and to my friend Bill Cassidy,” Warner told reporters. “This is a giant step backwards.”

Cassidy was one of two Republican doctors, along with Senate Majority Whip John Barrasso of Wyoming, who voiced concern Thursday that Kennedy’s actions may negatively impact public health.

“To me, what’s more important is that there are Republicans like Bill Cassidy, with medical degrees, that are beginning to call the question on the insanity that Robert Kennedy is spewing all over the place,” Bennet, D-Colo., told reporters. “I just hope that it won’t be too late.”

Cassidy left the Senate Finance Committee hearing room after questioning Kennedy on Thursday and told reporters several times that his exchange speaks for itself. Asked if he regrets his pivotal vote to confirm Kennedy to the position, Cassidy didn’t answer before disappearing into an elevator.

Within a few hours, Cassidy posted his portion of remarks from the hearing on X, asking why Trump hasn’t received a Nobel for Operation Warp Speed.