President Donald Trump on Monday signed an executive order calling for revamped childhood vaccine recommendations that promote his long-held belief that childhood shots should be spaced out into separate medical visits.

The order recommends separating the measles, mumps and rubella (MMR) vaccine into three different shots administered in separate visits, and directs the nation’s health department to improve vaccine research, according to a White House fact sheet first reported by The Daily Caller. Separate MMR vaccines for children are not currently available in the United States.

Speaking about the order at the Oval Office on Monday, Trump also said that one-year-olds should have their shots separated out into five separate visits, though it wasn’t clear whether he was talking about all the vaccines they receive or specific ones.

Public health experts have raised concerns that spacing out shots as Trump suggests can lead to an increased risk that children become infected with a vaccine-preventable disease before returning for another visit. Childhood vaccines—and how and when to give them in combination—go through rigorous studies, and safety tracking continues for years as the shots are used.

Even as the order calls for revised vaccine recommendations, states, not the federal government, have the authority to require vaccinations for schoolchildren. The order will advise states with school vaccine mandates to consider updating their laws to reflect the administration’s recommendations, the fact sheet said.

The specter of an outbreak of measles—one of the most contagious infections—has schools officials worried, not just for students but also for teachers, who are generally considered higher risk for exposure regardless of their immunization status.

More than 2,300 U.S. cases were documented by the end of July, a number that has already surpassed the 2025 tally.

Last December, Trump ordered the U.S. Department of Health and Human Services to review how peer nations approach vaccine recommendations and consider revising U.S. guidance accordingly. The department responded by cutting the number of vaccines it recommends for every child, a move that has since been blocked in court.

In the months leading up to Monday’s announcement, Trump’s administration had largely pivoted away from talking about vaccine policy in favor of less polarizing topics like healthy eating and efforts to lower drug prices ahead of November’s elections. Polls show most Americans still support school vaccine requirements, though Republicans are less likely than Democrats to see them as important.

Still, Trump has been fixated on connecting autism to vaccines. He has recently ramped up pressure on Health Secretary Robert F. Kennedy Jr. to identify the cause of autism, something Kennedy had pledged to do with new research unveiled last year. Trump publicly prodded the health secretary for an update on autism research in a Cabinet meeting last month.

“How are you doing on the autism research?” Trump asked.

“We will have an answer for you,” Kennedy said.

Scientific consensus and decades of studies have firmly concluded there is no link between childhood vaccines and autism. On Monday, Kennedy repeated his assertion that he believes an unknown environmental factor is to blame for rising autism diagnoses and said that his department will deliver research findings “as soon as they are ready.”

Monday’s order comes as school years are starting around the country and the nation contends with a measles outbreak that experts say could result in the U.S. losing its measles elimination status.