A Republican senator who also happens to be a doctor tore into President Trump's new childhood vaccine order on Sunday, calling it "just a stupid thing to do" that will leave more kids exposed to preventable disease.

Sen. Bill Cassidy (R-La.), chair of the Senate Health, Education, Labor and Pensions Committee, unloaded on ABC News' "This Week" over the order Trump signed last Monday directing that the combined measles-mumps-rubella (MMR) shot be broken into three separate single-disease injections given at separate visits — six doctor trips instead of two.

"This is inconvenient. It's going to contribute to an increased loss of income," Cassidy said, according to a report on the interview. "The president's proposal is going to end up with more children being sick."

"There's no evidence that vaccines causes autism, which I think is where this is supposed to come from." — Sen. Bill Cassidy

Trump invoked a debunked autism link when he signed the order, telling reporters at the time, "Nothing bad can happen from what we are doing. The worst thing that could happen would be nothing happens." Decades of research, including large-scale studies cited by the CDC, have found no connection between the MMR vaccine and autism.

A broken promise from Kennedy?

The clash carries extra weight because of Cassidy's own history with the administration. The Louisiana senator cast the pivotal vote in February 2025 confirming Robert F. Kennedy Jr. as Health and Human Services secretary, doing so only after Kennedy privately assured him he would not undermine the existing childhood vaccine schedule. Asked directly whether Kennedy had lied to him, Cassidy said the guarantees he was given had been broken, according to CNN's report on the Sunday show appearance.

Cassidy argued the switch to six separate appointments would hit working families hardest, forcing parents to burn through paid time off or lose wages, and could ultimately push insurance premiums higher as insurers cover triple the office visits. "As a physician who has seen people either die or get seriously ill from diseases that can be prevented by vaccines, this has the potential to decrease the protection that a child would receive," he said.

He went further, tying the policy to Trump's political standing: "This is why the president's poll numbers are down, because you've lost sight of affordability for the parent," Cassidy said, according to the Scripps News writeup of the interview.

Cassidy is no stranger to breaking with the president. He lost his 2026 Senate primary earlier this year to a Trump-backed challenger, a defeat that has left him with little political incentive to hold his tongue in his final months in office. His HELP Committee gavel gives him a platform to keep pressing the administration on the order as it takes effect.

The White House has not announced any change of course. The Justice Department and HHS did not immediately respond to requests for comment on Cassidy's remarks, and it remains unclear whether other Senate Republicans will join his criticism publicly in the coming days.