During the hearing, lawmakers called out Kennedy on his reluctance to advise parents to vaccinate their children as the nation faces a measles outbreak.

"My opinions about vaccines are irrelevant," Health and Human Services Secretary Robert F. Kennedy Jr. said during the House hearing.

Kennedy will appear before the House Appropriations Committee Wednesday morning and the Senate Health, Education, Labor, and Pensions (HELP) Committee in the afternoon. Last month, the HELP Committee called Kennedy to testify on the restructuring of the department.