As of Tuesday, 22 children and two adults had been infected, all of whom were unvaccinated, local officials said.

The federal order temporarily halts the Trump administration’s plans to slash $4 billion in overhead costs for research at universities and medical centers into diseases like cancer.

Robert F. Kennedy Jr., the nominee to lead the Department of Health and Human Services, made disputed claims before the Senate Committee on Health, Education, Labor and Pensions.

R.F.K. Jr. and others have blamed the ingredient for allergies and other illnesses. Scientists say it actually bolsters the immune response.

Scientific meetings were canceled, and research data on the bird flu outbreak was delayed, amid confusion over the directive.