In a Senate hearing that quickly turned contentious, Health and Human Services Secretary Robert F. Kennedy Jr. faced tough questions from Republican senators—many of whom are physicians—over his skepticism of COVID-19 vaccines and sweeping changes to federal vaccine policy. The September 4, 2025 hearing, held by the Senate Finance Committee, laid bare the deep divisions within the Republican Party and the broader American public over vaccines and public health leadership.
Senator Bill Cassidy of Louisiana, a practicing physician and a key figure in Kennedy’s confirmation just six months ago, set the tone with a pointed inquiry. "Mr. Secretary, do you agree with me that … the president deserves a Nobel Prize for Operation Warp Speed?" Cassidy asked, referencing former President Donald Trump’s initiative to rapidly develop COVID-19 vaccines—a program widely credited with saving millions of lives and reopening economies worldwide. Kennedy, somewhat surprisingly, replied, "Absolutely, senator," and called Operation Warp Speed "genius" for delivering a vaccine "perfectly matched to the virus at that time, when it was badly needed because there was low natural immunity and people were getting very badly injured by COVID."
That moment of agreement was fleeting. Cassidy, who praised Kennedy’s commitment to transparency, quickly turned critical, highlighting Kennedy’s cancellation of nearly $500 million in federally-funded mRNA vaccine research and his overhaul of the CDC’s vaccine advisory panel. Cassidy accused Kennedy of making it harder for Americans to access vaccines. "I would say effectively we're denying people vaccine," Cassidy said, echoing concerns from public health experts and his own medical colleagues.
Kennedy, for his part, defended his actions. He insisted he was not anti-vaccine: "Saying I'm anti-vaccine is like saying I'm anti-medicine. Well, I'm pro medicine, but I understand some medicines harm people. Some of them have risks. Some of them have benefits that outweigh those risks for certain populations. And the same is true with vaccines." Kennedy also reiterated his skepticism about the COVID-19 vaccine’s benefits for healthy people, stating, "there's no clinical data" supporting broad recommendations. He defended recent changes that narrowed FDA approval for COVID-19 vaccines to those over 65 or with underlying conditions, a move that public health officials argue could limit access and undermine public trust.
Senator John Barrasso of Wyoming, another physician, expressed his growing unease with Kennedy’s tenure. Barrasso cited polling showing that most Americans—over 80% of Trump voters included—want vaccine recommendations to come from trained physicians and public health experts. He reminded the committee, "Over the last 50 years, vaccines are estimated to have saved 154 million lives worldwide. I support vaccines. I'm a doctor. Vaccines work. Secretary Kennedy, in your confirmation hearings, you promised to uphold the highest standards for vaccines. Since then, I've grown deeply concerned."
Senator Roger Marshall of Kansas, also a physician, struck a more nuanced tone. While supporting vaccines, Marshall praised Kennedy’s "measured approach" and emphasis on transparency. Displaying a chart showing children receive 76 vaccine doses by age 18, Marshall said, "You're trying to empower parents here." He later argued on Fox News that not every person needs every vaccine, a sentiment Kennedy echoed in his remarks.
The hearing was not just a medical debate but a political minefield. Kennedy’s decision to stop recommending the COVID-19 vaccine for healthy children and pregnant women, his reshaping of the Advisory Committee on Immunization Practices, and the ouster of the new CDC director—who alleged pressure to preapprove vaccine recommendations—have all drawn sharp criticism. The FDA’s recent move to narrow approval for new COVID-19 vaccines from Pfizer, Moderna, and Novavax only added fuel to the fire.
Public health experts outside the government voiced alarm. Jennifer Nuzzo, director of Brown University's Pandemic Center, told reporters, "Kennedy’s views on vaccines are so far off any kind of normal factual place that many believe he is uniquely unqualified for the role of HHS secretary." Nuzzo praised Republican doctors for defending vaccine safety and efficacy, saying, "They may not always be senators, but they will always be doctors. And they have to uphold the oath that they've taken in becoming doctors." She warned that Kennedy’s policy changes could have serious impacts: "Vaccine recommendations are really important for deciding who is able to get vaccines. It's not just whether you'll be turned away at a pharmacy if you try to go get it. It's about whether your insurance will reimburse for it or if you have to pay out of pocket. And it's also about whether those pharmacies will even stock the vaccine in the first place."
The political risks were palpable, especially for Cassidy, who faces reelection next year and has drawn primary challengers. As Oklahoma State University politics professor Seth McKee noted, "It really speaks to his true intentions, which was he never should have voted for Kennedy in the first place." McKee suggested Cassidy’s earlier support for Kennedy may have been an attempt to regain favor with Trump, but the senator’s grilling of Kennedy at the hearing revealed his real concerns.
Meanwhile, President Trump has walked a careful line. In a recent meeting with his Cabinet, Trump called Operation Warp Speed "one of the greatest achievements ever," but he has also publicly demanded that vaccine companies justify their claims. "It is very important that the Drug Companies justify the success of their various Covid Drugs. Many people think they are a miracle that saved Millions of lives. Others disagree!" Trump wrote on Truth Social, urging companies to "show them NOW, to CDC and the public, and clear up this MESS, one way or the other!!!" Still, Trump praised Kennedy, telling ABC News that Kennedy "means very well" and "did very well" during the hearing. "He's got a different take and we want to listen to all of those things. I like the fact that he's different," Trump said.
Vaccine makers Pfizer and Moderna have stood firmly behind the science. Pfizer echoed Republican calls for Operation Warp Speed to be recognized as Nobel-worthy, while Moderna stated, "Since 2021, the real-world effectiveness and safety of the vaccines have been confirmed by governments and health systems around the world." Both companies pointed to hundreds of publicly available studies confirming vaccine safety and efficacy.
The White House also defended Kennedy in the wake of the hearing. Vice President JD Vance criticized Democratic senators for their attacks, and White House press secretary Karoline Leavitt insisted the administration was "championing gold-standard science." Yet, the hearing left many Americans wondering who to trust as public health leadership appears increasingly fractured.
As the dust settles, the Senate hearing has spotlighted not just the scientific debate over vaccines, but the political and institutional upheaval reshaping American public health. The clash between Kennedy’s skepticism, the medical consensus, and the political calculations of both parties is forcing a national reckoning over how—and by whom—public health policy should be made.
