This stance, along with concerns about budget cuts and political interference to the work of the CDC, prompted the resignation of four top agency leaders. On Thursday, dozens of CDC staff walked out of their Atlanta headquarters in support of Monarez and the other departed leaders.

The extraordinary turmoil at the CDC has provoked bipartisan alarm in Congress, earning the Trump administration a rare rebuke from normally slavishly loyal Republicans.

“She’s been on the job for only three weeks and I am very concerned and alarmed by this removal,” Susan Collins, the Republican senator from Maine, said of Monarez. Collins said there was “no basis” to remove the CDC director.

Bill Cassidy, another Republican senator who chairs the senate health committee, said that an upcoming meeting of the Department of Health and Human Services committee that advises on vaccine use should be postponed due to the attacks upon the CDC.