The White House has decided to withdraw the nomination of its pick to lead the Centers for Disease Control and Prevention, Dr. Dave Weldon, a Republican former congressman, just hours before he was to have appeared at a Senate confirmation hearing, according to a White House official and an administration official.

The officials, who spoke on condition of anonymity to disclose the decision, did not offer an explanation. But it became clear to the White House that Dr. Weldon did not have the votes in the full Senate to be confirmed, and Dr. Weldon said in an interview that he learned of the decision last night.

Dr. Weldon, 71, was to appear before the Senate health committee on Thursday at 10 a.m., the first time an agency director would have been subject to the confirmation process. The decision to withdraw the nomination was first reported by Axios.

His hearing was set to take place amid significant measles outbreaks in Texas and New Mexico, which have infected more than 250 people and claimed two lives; a flu season that led to record numbers of hospitalizations; and the potential for a bird flu epidemic.

He had repeatedly questioned the safety of the measles vaccine and criticized the C.D.C. for not doing enough to prove that vaccines are safe.

While in Congress, Dr. Weldon pushed to move the vaccine safety office away from C.D.C. control, saying the agency had a conflict of interest because it also purchases and promotes vaccines. He is also a staunch opponent of abortion.

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