(WASHINGTON) -- Health and Human Services Secretary Robert F. Kennedy Jr. was pressed on cuts to the National Institutes of Health (NIH), vaccine messaging and the firing of the former director of the Centers for Disease Control and Prevention (CDC) during a hearing on Tuesday.

The hearing before the House Committee on Energy and Commerce Subcommittee on Health marked the final session of four budget hearings before House lawmakers.

Rep. Lizzie Fletcher, D-Tex., said she was concerned about the loss of federal aid for health research in the Trump administration's budget request for fiscal year 2027.

"Secretary Kennedy, do you understand that cutting federally funded research as this budget does, will cede U.S. leadership on biomedical research to China and create national security and global competitiveness challenges for the United States?" Fletcher asked Kennedy.

Kennedy acknowledged that he shared Fletcher's concerns, as the biggest proposed cuts are to NIH and Administration for a Healthy America (AHA) programs.

"I don't want to cut NIH programs, [Office of Management and Budget Director] Russ Vought doesn't want to cut NIH programs, but we have a $35 trillion debt," Kennedy said.

"We have been asked to cut across the board at HHS, 12% of our $100 million budget and so we're making cuts that are painful," he told Fletcher.

Rep. Marc Veasey, D-Tex., described Kennedy as the most "anti-vax" figure in his lifetime. He suggested that Kennedy's history of rhetoric denouncing vaccines is correlated with an uptick in measles cases.

Two unvaccinated school-aged children died last year from measles -- the first U.S. deaths from measles in a decade.

Kennedy has long sown doubt in the safety and effectiveness of the measles, mumps, rubella (MMR) vaccine. Despite being a required vaccine in all states to attend public school, rates have been steadily decreasing over the last decade, CDC data shows.