NEW YORK (AP) — The nation’s top public health agency was left reeling Thursday as the White House worked to expel the Centers for Disease Control and Prevention director and replace her with Health Secretary Robert F. Kennedy Jr.’s current deputy.

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

Two administration officials said Jim O’Neill, the second-in-command at the Department of Health and Human Services, would supplant Susan Monarez, a longtime government scientist. O’Neill, who also served at the federal health department under President George W. Bush, does not have a medical background.

It’s unclear if O’Neill would stay in both roles.

A flashpoint is expected in the coming weeks as a key advisory committee, which Kennedy has reshaped with vaccine skeptics, is expected to issue new recommendations on immunizations. The panel is scheduled to review standard childhood shots for measles, hepatitis and other diseases.

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

Kennedy has not explained the decision to oust Monarez less than a month after she was sworn in, but warned there may be more turnover.

“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,” he said at a news conference in Texas.

The White House has only said that Monarez was “not aligned with” President Donald Trump’s agenda.

Monarez’s lawyers said she refused “to rubber-stamp unscientific, reckless directives and fire dedicated health experts.” She is fighting her dismissal.

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.