NEW YORK — Jim O’Neill, a top deputy to Health Secretary Robert F. Kennedy Jr., will serve as acting director of the Centers for Disease Control and Prevention, according to an administration official.

The official requested anonymity to discuss a personnel change that has not been formally announced. The administration wants O’Neill to replace Susan Monarez, whom the White House is trying to remove only a month after starting the job.

Monarez is fighting to keep her job. Her removal has left the nation’s top public health agency reeling and three senior officials were escorted from its headquarters Thursday.

The turmoil triggered rare bipartisan alarm as Kennedy tries to advance anti-vaccine policies that are contradicted by decades of scientific research.

The chaos comes weeks before a key advisory committee, which Kennedy has reshaped with vaccine skeptics, is expected to meet to issue new recommendations on immunizations.

Two Republican senators called for congressional oversight and some Democrats said Kennedy should be fired. He is scheduled to testify on Capitol Hill on Sept. 4.

Kennedy has not explained the decision to oust Susan Monarez as CDC director less than a month after she was sworn in, but warned that more turnover could be coming.

“There’s a lot of trouble at the CDC and it’s going to require getting rid of some people over the long term, in order for us to change the institutional culture,” Kennedy said at a news conference in Texas.

The White House has only said that Monarez was “not aligned with” President Donald Trump’s agenda. There is no word on when a replacement could be named.

Monarez’s lawyers said that she refused “to rubber-stamp unscientific, reckless directives and fire dedicated health experts.” She is fighting her dismissal, saying the decision must come directly from Trump, who nominated her in March.

The saga began Wednesday night with the administration’s announcement that Monarez would no longer lead the CDC. In response, three officials — Dr. Debra Houry, Dr. Demetre Daskalakis and Dr. Daniel Jernigan — resigned from senior roles at the agency.

The officials returned to the office Thursday to collect their belongings, and staff members at the beleaguered agency had planned to gather in the afternoon to applaud them as they left the Atlanta campus. But their removal by security personnel earlier in the morning squelched those plans, according to current and former employees.

Houry and Daskalakis told The Associated Press that Monarez had tried to guard against political meddling in scientific research and health recommendations.

“We were going to see if she was able to weather the storm. And when she was not, we were done,” Houry said. She had been the agency’s deputy director and chief medical officer.

Daskalakis resigned as head of the National Center for Immunization and Respiratory Diseases and Jernigan from the National Center for Emerging and Zoonotic Infectious Diseases

If removed, Monarez will be the shortest-serving director since the CDC was founded in 1946, exacerbating a leadership vacuum that has persisted since Trump took office. He initially chose David Weldon, a former Florida congressman who is a doctor and vaccine skeptic, but yanked the nomination in March.

Monarez, a longtime government scientist, was tapped next to lead the $9.2 billion agency while she was serving as its interim director. But questions immediately emerged within Kennedy’s circle about her loyalty to the “Make America Healthy Again” movement, especially given her previous support of the COVID-19 vaccines that Kennedy has routinely criticized.

Kennedy rarely mentioned Monarez by name in the way he did other health agency leaders such as Mehmet Oz of the Centers for Medicare and Medicaid Services or Marty Makary of the Food and Drug Administration.

A flashpoint has been Kennedy’s handling of the CDC’s advisory vaccine committee, which he has tried to reshape since taking over the Department of Health and Human Services.

The panel is expected to meet next month, and Sen. Bill Cassidy, R-La., said any recommendations issued then will be “lacking legitimacy.”

“Serious allegations have been made about the meeting agenda, membership, and lack of scientific process being followed,” said Cassidy, who heads the Senate committee overseeing Kennedy’s department. He added that “these decisions directly impact children’s health and the meeting should not occur until significant oversight has been conducted.”

Cassidy, a doctor, provided crucial support for Kennedy’s nomination after saying Kennedy had assured him that he would not topple the nation’s childhood vaccination program.

The Advisory Committee on Immunization Practices is a group of outside experts who make recommendations to the CDC director on how to use vaccines. The recommendations are then adopted by doctors, school systems, health insurers and others.

Kennedy is a longtime leader in the anti-vaccine movement, and in June, he abruptly dismissed the entire panel, accusing members of being too closely aligned with manufacturers. He replaced them with a group that included several vaccine skeptics and then he shut the door to several doctors organizations that had long helped form vaccine recommendations.

Houry and Daskalakis said Monarez had tried to make sure scientific safeguards were in place.

For example, she tried to replace the official who coordinated the panel’s meetings with someone who had more policy experience. Monarez also pushed to have slides and evidence reviews posted weeks before the committee’s meetings and have the sessions open to public comment, Houry said.

HHS officials nixed that and called Monarez to a meeting in Washington on Monday, Houry said.

Daskalakis described the situation as untenable.

“I came to the point personally where I think our science will be compromised, and that’s my line in the sand,” he said.

The Associated Press Health and Science Department receives support from the Howard Hughes Medical Institute’s Department of Science Education and the Robert Wood Johnson Foundation. The AP is solely responsible for all content.

Copyright 2025 Associated Press. All rights reserved. This material may not be published, broadcast, rewritten, or redistributed.