Former Centers for Disease Control and Prevention (CDC) Director Susan Monarez took her fight to Capitol Hill on Wednesday, delivering explosive testimony that cast her firing as a direct result of her refusal to “betray science.”

Monarez, appearing before the Senate Committee on Health, Education, Labor and Pensions, accused Health and Human Services Secretary Robert F. Kennedy Jr. of ordering her to rubber-stamp vaccine policy changes without scientific evidence and to purge senior CDC officials. When she refused, she said, she was pushed out of her post just 29 days after Senate Republicans had unanimously confirmed her.

“He directed me to commit in advance to approving every advisory panel recommendation, regardless of the evidence,” Monarez told lawmakers. “He also directed me to dismiss career scientists overseeing vaccine policy without cause. I could not do either, and that is the true reason I was fired.”

The testimony, her first public appearance since her removal, immediately intensified Washington’s most combustible health and political controversy. Kennedy, a longtime vaccine skeptic elevated by the Trump administration to lead HHS, has already triggered resignations, protests, and a storm of criticism over his reshaping of U.S. vaccine policy.

Monarez described a “tense and unproductive” meeting with Kennedy where he pressed her to align with his agenda. According to her account, Kennedy admitted there was “no science or data” to support his planned overhaul of the childhood vaccine schedule but insisted she accept it anyway. “He was very upset,” she said. “The entire meeting was tense.”

Her refusal to comply, she argued, cost her the job.

Kennedy, testifying earlier this month before another Senate committee, flatly denied the accusations. He claimed Monarez told him she was “untrustworthy” and effectively offered her resignation. In a fiery back-and-forth with Sen. Elizabeth Warren, Kennedy defended his decision: “If you had an employee who told you they weren’t trustworthy, would you keep them?”

But Monarez’s testimony has gained credibility through the wave of resignations that followed her firing. Debra Houry, the CDC’s chief medical officer, stepped down along with three other top officials, all citing Kennedy’s interference. Their departures, coupled with Monarez’s account, have fueled fears of an ideologically driven purge inside the nation’s leading public health agency.

Sen. Bernie Sanders praised Monarez as a public servant punished for her principles. “She stood up for protecting the well-being of the American people, and for that she was fired,” Sanders said, blasting what he called Kennedy’s “dangerous war on science.”

Even Republicans are showing cracks in support. Senate Majority Leader John Thune said Kennedy must “take responsibility” for Monarez’s removal, while Sen. Susan Collins admitted she saw “no justification.” Sen. Bill Cassidy, the Republican chair of the committee, questioned whether the Senate had “failed” in confirming Kennedy without greater scrutiny.

Monarez herself insisted the stakes go beyond her career. “Today should not be about me,” she testified. “Today should be about the future of trust in public health. I could have stayed silent and kept the office, but I would have lost the one thing that cannot be replaced: my integrity.”

Since taking over HHS, Kennedy has canceled $500 million in contracts for mRNA vaccines, reshaped COVID-19 vaccine guidance, and replaced the CDC’s vaccine advisory committee with his own appointees, some of whom share his skepticism of vaccines. The Food and Drug Administration recently narrowed approval for updated COVID shots to Americans over 65 or those with underlying conditions, a dramatic departure from prior recommendations.

With Kennedy’s new advisory committee set to review childhood vaccines such as MMRV and RSV in the coming weeks, Monarez issued a stark warning: “There is real risk that recommendations could be made restricting access to vaccines for children and others in need without rigorous scientific review.”

Her testimony underscored a bitter national divide: whether vaccine policy will continue to be driven by data and evidence, or by political ideology.