The White House withdrew the nomination of former Florida congressman Dr. David Weldon to lead the Centers for Disease Control and Prevention because he wasn’t assured of getting enough Republican support to be confirmed.

The Republican-controlled Senate health committee announced Thursday morning that it was canceling a planned hearing on Weldon’s nomination — less than an hour before it was scheduled to begin.

A White House assistant told Weldon on Wednesday night that his nomination was being withdrawn because “there were not enough votes to get me confirmed,” the ex-congressman said in a statement.

Sen. Lisa Murkowski, an Alaska Republican and committee member, told reporters she had relayed her concerns about Weldon’s vaccine skepticism both to him directly and to the White House. Two other Republicans who have voiced concerns about the administration’s direction on vaccines, Sens. Bill Cassidy and Susan Collins, said they had not decided whether to support or oppose his confirmation.

Weldon was considered to be closely aligned with Robert F. Kennedy Jr., the U.S. health secretary who for years has been one of the nation’s leading anti-vaccine activists.

Weldon, 71, is an Army veteran and internal medicine doctor whose main claim to fame was representing a central Florida district in Congress from 1995 to 2009.

He was a leader of a Congressional push for research into autism’s causes, which began around 2000. But Weldon rejected studies that found no causal link between childhood vaccines and autism, and accused the CDC of short-circuiting research that might show otherwise.

“My big sin was that as a congressman 25 years ago I had the temerity to take on the CDC and big Pharma” on childhood vaccine safety issues, Weldon wrote in his four-page statement.

Weldon said Kennedy told him that Collins, a Maine Republican, had expressed reservations about the nomination. He also believes that Cassidy, the Louisiana Republican who chairs the health committee, was against his nomination.

Collins said: “I had some reservations, but I certainly had not reached a final judgment.”

Cassidy said he didn’t ask for Weldon’s withdrawal and was surprised by it.

“I was looking forward to the hearing,” Cassidy said in a statement. “His poor response to this situation shows that the pressures of being CDC director would have been too much.”

Sen. Patty Murray, who is also on the health committee, said she had serious concerns about Weldon after meeting with him.

“I was deeply disturbed to hear Dr. Weldon repeat debunked claims about vaccines,” the Washington Democrat said in a statement. “It’s dangerous to put someone in charge at CDC who believes the lie that our rigorously tested childhood vaccine schedule is somehow exposing kids to toxic levels of mercury or causing autism.”

The White House did not issue a statement explaining the withdrawal, and Trump did not address it during a Thursday afternoon press availability. The Department of Health and Human Services did not respond to a request for comment.

With a $9.2 billion core budget, the Atlanta-based CDC is charged with protecting Americans from outbreaks and other public health threats.

For decades it enjoyed a sterling reputation as a global leader on disease control and a reliable source of health information, boasting some of the top experts in the world. But the agency came under attack during the COVID-19 pandemic, repeatedly faulted for how it handled communications, masking guidance and others aspects of its pandemic response.

This week, Cassidy and other Republican leaders launched a working group to examine potential legislative reforms for the agency, which has been swept up in the government-wide job-cutting push led by the president and his billionaire adviser Elon Musk.

Weldon was to be the first CDC director nominee to have to go through Senate confirmation — the result of a provision in a law passed during the Biden administration. The agency’s 20 previous directors were all appointed.

He becomes the third Trump administration nominee who didn’t make it to a confirmation hearing. Previously, former U.S. Rep. Matt Gaetz withdrew from consideration for attorney general and Chad Chronister for the Drug Enforcement Administration.