U.S. Health and Human Services Secretary Robert F. Kennedy Jr., testifies before a Senate Finance Committee hearing on President Donald Trump's 2026 health care agenda, on Capitol Hill in Washington, D.C., U.S., September 4, 2025. REUTERS/Jonathan Ernst

By Ahmed Aboulenein

WASHINGTON (Reuters) -U.S. Senators on both sides of the aisle sought to show a division between Health Secretary Robert F. Kennedy Jr.'s stance on COVID vaccines and Operation Warp Speed, President Donald Trump's successful first-term initiative to help quickly develop effective shots against the virus.

Republican U.S. Senator Bill Cassidy of Louisiana praised Trump for the project, which accelerated the development, manufacturing, and distribution of COVID-19 vaccines in 2020.

Cassidy said Trump deserves the Nobel Peace Prize for the achievement and asked Kennedy if he agreed. Kennedy said he did.

Why then has Kennedy said the vaccines had killed more people than COVID? Cassidy asked during a Senate Finance Committee hearing. Kennedy denied making the statement and initially would not agree that the vaccines saved lives, but in a later exchange acknowledged the shots prevented deaths but that he could not quantify that.

COVID vaccines in the first year of their use saved some 14.4 million lives globally, according to a study published in The Lancet Infectious Diseases journal.

Republican John Barrasso of Wyoming, who like Cassidy is a physician, adopted the same tactic, underscoring the tightrope Republicans critical of Kennedy need to walk in order to push back against his vaccine policies without criticizing Trump.

"Secretary Kennedy, in your confirmation hearings you promised to uphold the highest standards for vaccines. Since then, I've grown deeply concerned," said Barrasso.

"The public has seen measles outbreaks, leadership in the National Institutes of Health questioning the use of mRNA vaccines, the recently confirmed Director of Centers for Disease Control and Prevention fired," the senator added.

Kennedy, under fiery questioning from Democratic Senator Ron Wyden and others, also defended his ousting of CDC Director Susan Monarez, adding that he might need to fire even more people at the agency.

Trump fired Monarez after she resisted changes to vaccine policy advanced by Kennedy that she believed contradicted scientific evidence, further destabilizing the already embattled agency.

In an opinion piece in the Wall Street Journal on Thursday, Monarez said she had been directed to preapprove vaccine recommendations, and that her ouster was part of a broader push to weaken U.S. vaccine standards.

Kennedy said that he had never told Monarez she needed to preapprove decisions.

CALLS FOR KENNEDY RESIGNATION

Kennedy said the CDC during the COVID-19 pandemic had lied to Americans, pointing to recommendations on mask wearing, vaccine boosters and social distancing and statements that the vaccine would prevent transmission.

"I need to fire some of those people and make sure this doesn't happen again," Kennedy said.

During the COVID pandemic, the CDC came under fire as Americans became frustrated, particularly with school closures, although its changing recommendations were based on past experience with virus transmission and what was known about the novel coronavirus at the time.

By late 2021, as the Omicron variant spread quickly and more real-world data on the vaccines accumulated, the CDC acknowledged the shots could not stop COVID infection and transmission, but were highly effective in preventing severe cases, hospitalizations and death.

Since taking the job, Kennedy has made a series of controversial changes to U.S. vaccine policy, including narrowing who is eligible for COVID shots and firing all 17 expert members of a CDC vaccine advisory panel, choosing some fellow anti-vaccine activists to replace them.

Kennedy has faced criticism from some Republicans and calls to resign by some Democrats since Monarez's firing, which triggered the resignations of four senior agency officials who cited anti-vaccine policies and misinformation pushed by Kennedy and his team.

Wyden called for his resignation on Thursday at the beginning of the hearing, as have other senators and over 1,000 current and former health employees.

Cassidy, who chairs the Senate Health, Education, Labor, and Pensions Committee, has said the CDC upheaval warrants oversight. He was the deciding vote during Kennedy's confirmation process after receiving assurances the long-time anti-vaccine crusader would not interfere with vaccine policy.

On Thursday he pressed Kennedy on his decision to cancel $500 million in funding for research on the mRNA technology used in making the most widely used COVID vaccines.

(Reporting by Ahmed Aboulenein; Editing by Bill Berkrot and Caroline Humer)