President Trump has ordered a reduction in childhood vaccines — publicly faulting the shots for an increase in autism cases — even as the nation’s top health official, Robert F. Kennedy Jr., has failed to produce evidence linking vaccinations to the disorder.

While the executive order released Aug. 10 does not directly mention autism, Mr. Trump’s demand to limit vaccine recommendations has puzzled leading medical groups, doctors, and political analysts alike. The directive landed less than 90 days before midterm elections, which Mr. Trump’s own pollsters have warned could be jeopardized by anti-vaccine rhetoric.

“The political timing, particularly for members on the Republican side in swing districts, is not good,” said Larry Bucshon, a former Republican congressman and retired doctor.

Mr. Trump’s willingness to gamble on the issue underscores the president’s impatience for his health secretary to deliver on a promise that he’d pinpoint a culprit for the sharp rise in autism diagnoses.

After more than a year, Kennedy and his close, anti-vaccine allies have blown past a deadline to turn up definitive answers in a multimillion-dollar research mission shrouded in secrecy, leaving the president to recycle debunked notions as he publicly assaults vaccines.

“This is about the most closed project that I’ve ever heard of,” Helen Tager-Flusberg, a renowned psychologist who runs the Coalition of Autism Scientists, said of Kennedy’s autism research efforts. “They’re treating it like the Manhattan Project in the 1940s. This is as opaque as it could possibly be.”

The White House did not answer questions about what research is informing the president’s opinions or which vaccines he believes could be linked to autism.

The Department of Health and Human Services said the president’s action builds on the agency’s January announcement that it was reassessing the nation’s vaccine schedule and recommended reducing childhood immunizations based on peer countries’ guidance. However, no other peer country separates the measles, mumps, and rubella vaccine as the president has now ordered.

“As the secretary said, HHS will examine every biologically plausible hypothesis, follow the evidence wherever it leads, and make findings and actions available as they are ready,” HHS spokesperson Emily Hilliard said in an email.

Trump dreams of a “big day”

Mr. Trump especially has been enamored with finding autism’s cause, saying in August 2025 that it will be “such a big day” after Kennedy assured his boss that he had identified “clearly, almost certainly” factors causing autism that would soon be publicly revealed.

Decades of existing research and scientific studies show genetics is a leading factor. Environmental factors — including prenatal exposure to pollution, the age of the father, and maternal health — can also play a role.

But Kennedy has flatly rejected that science, often calling autism a “preventable disease.” As health secretary, he has spent millions of taxpayer dollars looking for root causes in a research effort that’s offered no public status updates and few details about who, or even which agency, is leading the effort.

Prominent autism advocacy groups, scientists, and researchers have not been consulted on the project. Nor have career scientists working at the federal health agencies, according to two officials KFF Health News is not naming because they were not authorized to speak on the record about the matter.

Requests to meet with Kennedy on the issue have been ignored, said Delancy Allred, public policy manager at the Autism Society. Allred said that other federal agencies, such as the Department of Education, have engaged more directly with leading autism advocacy groups during meetings.

“No one has gotten to Kennedy. No one has gotten to the secretary level, that I’m aware of,” Allred said. “I think he likes to isolate himself with folks that are in his domain and group.”

Indeed, Kennedy has relied on allies, who’ve joined him over the years on a crusade against childhood vaccines, to lead the agency’s autism research and strategy efforts. It’s a top priority for his closest adviser, Stefanie Spear, a former environmental activist and longtime confidant, according to the unnamed sources. Spear did not respond to requests to talk about the autism study.

William “Reyn” Archer III — a former Texas health official, trained obstetrician-gynecologist, and vaccine critic whom Kennedy hired as a senior adviser — has spent months acquiring Americans’ medical records for political appointees to research a link between vaccines and autism. The National Institutes of Health under Mr. Trump has also issued about $50 million in grants to scientists at universities around the country for autism research, although most of the studies are not scheduled to be completed for a few years.

In January, Kennedy also restocked the Interagency Autism Coordinating Committee — an under-the-radar but influential group — with a full new slate of 21 members. His appointees include parents of autistic children, vaccine skeptics, and a doctor who was sued for “dangerous” autism treatment. It has met only once during Mr. Trump’s current term.

Late last month, the committee abruptly dropped a 336-page strategic plan that echoes some of Kennedy’s talking points: Federal researchers have focused too much on genetic links to autism, the plan suggests.

Diagnoses of autism, a neurodevelopmental condition that affects how people communicate and behave, have increased roughly fivefold over the past couple of decades. The increase is attributed partly to greater awareness and screening, a more expansive definition of the disorder, and parents having children at a later age, various studies show.

Mr. Trump and Kennedy have falsely claimed that the rise in diagnoses is isolated among American children — though diagnoses have dramatically risen in both older adults and children around the globe.

Despite his efforts to launch new research, Kennedy has provided Mr. Trump with no conclusive explanation for these increases. Mr. Trump began publicly pressing his health secretary on the issue last month during a Cabinet meeting when he asked Kennedy: “How are you doing on the autism research?”

Kennedy replied, “We will have an answer for you,” before Mr. Trump cut him off.

“That is so important,” the president pressed.

Kennedy’s vaccine agenda has been stymied, in part, by the White House’s infighting. Behind the scenes, White House officials have spent months waving Kennedy off his vaccine agenda amid a historic wave of measles infections.

With his Aug. 10 Oval Office signing, Mr. Trump made clear Kennedy’s vaccine agenda remains a top priority. The signing also came at a politically convenient moment: The Senate broke for a five-week recess, just after the White House secured the votes it needed for crucial confirmations of Centers for Disease Control and Prevention Director Erica Schwartz and Attorney General Todd Blanche.

Kennedy misfires

Many of Kennedy’s claims so far on autism have not withstood scientific scrutiny. Last year, the health secretary said Tylenol use in pregnancy can lead to autism. A major new study in the peer-reviewed journal JAMA debunked the connection — a political stumble for Mr. Trump, who had publicly repeated the claim and urged women not to take the pain reliever.

Kennedy also offered that circumcision could be a cause during a Cabinet meeting in October. A large study published in August in JAMA Pediatrics found no such evidence. He said on The Tucker Carlson Show in 2025 that a hidden CDC study linked the hepatitis B vaccine to a 1,135% increase in autism. However, his remarks misrepresented the findings; the Belgian researcher he referred to later studied thimerosal exposure in vaccines and found no increased autism risk.

And Kennedy canceled millions of dollars in funding for research that was underway to search for autism’s causes, including potential environmental sources.

Pressed on details about the administration’s work studying autism, NIH Director Jay Bhattacharya admitted that no conclusion had been reached during an interview on “Face the Nation with Margaret Brennan.”

“If you ask me, as a scientist, do I know why we’ve seen this rise in autism? I’ll tell you I don’t know the answer to that question,” he said Aug. 9.

Seated at his desk in the Oval Office the next day, Mr. Trump repeatedly made the connection between autism and vaccines just before signing the executive order calling for fewer childhood shots.

Appearing alongside Mr. Trump, Kennedy seemed intent on quelling expectations that HHS would produce results expeditiously. He told the president he was racing to find answers before the end of his term.

“Mr. President, you have told us you want answers. So do I,” Kennedy said. “We have just over two years to finish the work, and I know you’re impatient, and we are moving with an urgency that that deadline demands.”

While Mr. Trump has repeatedly claimed there’s a link between autism and vaccines, he has not revealed which of the routine vaccinations he believes might be to blame, and he praised the polio vaccine as “amazing” during the White House event.

White House officials declined to answer questions about the status of Kennedy’s efforts to identify the cause of autism during a call a few hours later.

KFF Health News is a national newsroom that produces in-depth journalism about health issues and is one of the core operating programs at KFF — the independent source for health policy research, polling, and journalism.