WASHINGTON (AP) -- Fired Centers for Disease Control and Prevention director Susan Monarez will tell senators that Health Secretary Robert F. Kennedy Jr. pressured her to endorse new vaccine recommendations before seeing scientific evidence, according to a copy of the testimony she plans to give during a Wednesday hearing.

According to a copy of the prepared remarks, obtained Tuesday by The Associated Press, Monarez will tell senators that Kennedy gave her an ultimatum: "Preapprove" new vaccine recommendations from a controversial advisory CDC panel that Kennedy has stocked with some medical experts who doubt vaccine safety or be fired. That panel is expected to vote on new vaccine recommendations later this week.

Monarez, initially handpicked by Kennedy and nominated by President Donald Trump, was fired just weeks into the job over disagreements on vaccine policies. She is set to appear before the Senate's powerful health committee to discuss her firing.

"Even under pressure, I could not replace evidence with ideology or compromise my integrity," Monarez will say in her opening testimony to senators. "Vaccine policy must be guided by credible data, not predetermined outcomes."

She said she was "fired for holding the line on scientific integrity."

Monarez also notes that Kennedy directed her to fire a number of high-ranking CDC officials without cause.

The Senate hearing will focus on the impact the turmoil at the nation's leading public health agency, which is responsible for making vaccine recommendations to the public, will have on children's health. It will also undoubtedly serve as an opportunity for Monarez and former Chief Medical Officer Debra Houry, who will also testify before the committee, to respond to a number of Kennedy's contentious claims about their final days at the agency.

Kennedy has denied Monarez' accusations that he ordered "rubber-stamped" vaccine recommendations.

He has described Monarez as admitting to him that she is "untrustworthy," a claim Monarez has denied through her attorney. He did, however, acknowledge during a testy Senate hearing earlier this month that he ordered Monarez to fire several top officials at the CDC.

The Senate hearing is taking place just a day before the vaccine panel starts its two-day session in Atlanta to discuss shots against COVID-19, hepatitis B and chickenpox. It's unclear how the panel might vote on the recommendations, though members have raised doubts about whether hepatitis B shots administered to newborns are necessary and have suggested that COVID-19 recommendations should be more restricted.

The CDC director must endorse those recommendations before they become official. Health and Human Services Deputy Secretary Jim O'Neill, now serving as the CDC's acting director, will be responsible for that.

Monarez and Houry are expected to face tense questions from Republicans over the CDC's vaccine recommendations and COVID-19 policies. Democrats, meanwhile, are likely to seek more information on Kennedy's approach to vaccines.

The health committee's hearing will be overseen by Republican Sen. Bill Cassidy of Louisiana, a physician who cast a key vote for Kennedy's confirmation. He has expressed concern about "serious allegations" at the CDC and has called for oversight, without blaming Kennedy.

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Associated Press writers Mike Stobbe in New York and Lauran Neergaard in Washington contributed.

Fired CDC chief will testify Kennedy pressed her to endorse vaccine recommendations without evidence