This is a KFF Health News story.

Ann Bauer, a researcher who studies Tylenol and autism, felt queasy with anxiety in the weeks leading up to the White House’s much-anticipated autism announcement.

In August, Bauer and her colleagues published an analysis of 46 previous studies on Tylenol, autism and attention-deficit/hyperactivity disorder. Many found no link between the drug and the conditions, while some suggested Tylenol might occasionally exacerbate other potential causes of autism, such as genetics.

Bauer, an epidemiologist at the University of Massachusetts-Lowell, and her team called for more judicious use of the drug until the science is settled.

On Monday, President Donald Trump stood beside Health and Human Services Secretary Robert F. Kennedy Jr. for what he called a “historic” announcement on autism. “If you’re pregnant, don’t take Tylenol, and don’t give it to the baby after the baby is born,” Trump said. “There are certain groups of people that don’t take vaccines and don’t take any pills that have no autism,” he added, without providing evidence. “They pump so much stuff into those beautiful little babies, it’s a disgrace.”

A fact sheet released alongside the White House briefing cited Bauer’s analysis. But she was alarmed by Trump’s comments. If prenatal Tylenol has any association, which it may not, it would help account for only a fraction of cases, she said. Further, research has not deeply examined Tylenol risks in young children, and many rigorous studies refute a link between vaccines and autism.

Bauer worries such statements will cut both ways: People may put themselves at risk to avoid vaccines and Tylenol, the only safe painkiller for use during pregnancy. And she frets that scientists might outright reject her team’s measured concerns about Tylenol in a backlash against misleading remarks from Trump and other members of his “Make America Healthy Again” movement.

“I’m really concerned about how this message is going to play out,” she said. “It’s a sound-bite universe, and everyone wants a simple solution.”

Autism experts at the Centers for Disease Control and Prevention were neither consulted for the White House’s long-awaited autism announcement nor asked to review a draft of the findings and recommendations, CDC scientists told KFF Health News, which agreed not to identify them because they fear retaliation.

“Typically, we’d be asked to provide information and review the report for accuracy, but we’ve had absolutely no contact with anyone,” one CDC researcher said. “It is very unusual.”

Trump and Kennedy promised this year that under their leadership the federal government would swiftly figure out what causes autism. Scientists who work in the field have been skeptical, noting that decades of research has shown that no single drug, chemical, or other environmental factor is strongly linked to the developmental disorder. In addition, both Trump and Kennedy have repeated the scientifically debunked notion that childhood vaccines may cause autism.

Helen Tager-Flusberg, director of the Center for Autism Research Excellence at Boston University, called Trump’s comments dangerous. Fevers can harm the mother and the developing fetus, she said, adding that fevers are more strongly associated with autism than Tylenol.

In an emailed response to queries, HHS spokesperson Andrew Nixon said, “We are using gold-standard science to get to the bottom of America’s unprecedented rise in autism rates.”

White House spokesperson Kush Desai wrote, “President Trump pledged to address America’s rising rate of autism, and to do so with Gold Standard Science.”

Had CDC scientists been allowed to brief Kennedy, they say they would have cautioned that simple fixes won’t make a dent in the number of autism cases in the United States: As many as 1 in 31 8-year-old children had autism spectrum disorder in 2022.

Systemic changes, such as regulations on air pollution, which has been linked to asthma and developmental disabilities including autism, and assistance for parents of disabled children, could improve lives for far more Americans with autism and other conditions than actions taken by the Trump administration on Sept. 22, researchers say.

One federal action is to consider updating the label on Tylenol and to “encourage clinicians to exercise their best judgment in use of acetaminophen for fevers and pain in pregnancy by prescribing the lowest effective dose for the shortest duration.” The American College of Obstetricians and Gynecologists already recommends acetaminophen “as needed, in moderation, and after consultation with a doctor.”

‘Political crusade’

Despite Kennedy’s many years of speaking about autism, he rarely cites credible autism research or expert recommendations, Tager-Flusberg said. Instead, Kennedy repeats fringe, scientifically debunked theories linking vaccines to autism, despite rigorous studies published in peer-reviewed journals that refute a link.

At the Sept. 22 briefing, Trump said he spoke with Kennedy about autism 20 years ago: “We understood a lot more than a lot of people who studied it,” he said. Ahead of Trump’s first term in 2017, Kennedy said he met with the president to consider a commission on vaccine safety and autism. It didn’t happen then. But soon after Kennedy was confirmed as health secretary, he called autism “preventable,”pointed to; “environmental toxins,” and contradicted the results of a CDC study finding that the main driver of rising autism diagnoses was that doctors increasingly recognize the disorder.

At a televised Cabinet meeting in April, Kennedy told Trump, “By September, we will know what has caused the autism epidemic and we’ll be able to eliminate those exposures.”

“You stop taking something, you stop eating something, or maybe it’s a shot,” Trump replied.

“He is on a political crusade,” Tager-Flusberg said of Kennedy, adding that vaccines, Tylenol, aluminum, and food dyes make for simple targets to rally against. “We know genetics is the most significant risk factor,” she said, “but you can’t blame Big Pharma for genetics, and you can’t build a political movement on genetics research and ride to victory.”

“RFK makes our work harder,” said Peter Hotez, a vaccine researcher and the author of a book about his autistic daughter, “Vaccines Did Not Cause Rachel’s Autism.” He said the book stemmed from conversations with Kennedy in 2017, in which Hotez shared studies pinpointing more than a hundred genes linked to autism, and research into the complex interplay between genetics, biological processes, and things that children and fetuses encounter during development.

“I sat down with him and explained what the science says, but he was unwilling or incapable of thinking deeply about it,” Hotez said. “He is extremely careless.”

In addition to its focus on Tylenol, the White House said it would move to update “prescribing information” on leucovorin — a medication related to the B vitamin folate — to reflect its use as an autism treatment. A small clinical trial in 2012-13 suggested the drug may help treat language problems in some children with autism. Tager-Flusberg said the findings warrant further study but clarified these were “old data, not a breakthrough.”

Likewise, studies finding a modest association between autism and prolonged Tylenol use were published years ago. Researchers have suggested the medicine might occasionally exacerbate factors associated with autism, such as genetics and oxidative stress, a biological condition that occurs for a variety of reasons that scientists are still unraveling.

Still, these studies couldn’t rule out the possibility that fevers prompting women to take Tylenol, rather than the medicine itself, might instead be to blame. Fevers and infections — including those prevented by vaccines — have also been linked to autism.

Nonetheless, Bauer’s recommendation would be to pause before taking acetaminophen while pregnant blanket advice that doctors give for all medications during that period, but which may be ignored. “Try to alleviate discomfort in some other ways, like with a cold compress, hydration, or massage, before taking it,” Bauer said.

She welcomed the White House’s motion to consider labeling Tylenol to emphasize judicious use of the drug but worries about how the MAHA movement might distort a careful message. On Sept. 2, the right-wing news outlet One America News Network posted an interview with newly appointed CDC vaccine adviser Robert Malone, writing that Malone “speculates RFK Jr. may have an important announcement this month regarding a potential link between Tylenol, multiple vaccinations and autism in children.”

“I was sick to my stomach,” Bauer said, concerned that Kennedy would link her study to discredited theories, causing doctors and scientists to reject her far more measured work.

‘The boy who cried wolf’

Several medical and scientific associations have called for Kennedy’s removal or resignation. Many scientists are skeptical of what he says because much of it has been misleading or wrong. For example, he’s said HIV isn’t the only cause of AIDS (it is), that antidepressant drugs cause mass shootings (they don’t), that older adults don’t have severe autism (some do), that the measles vaccine causes brain swelling (it doesn’t), that covid vaccines were the deadliest vaccines ever made (they aren’t), that vaccines aren’t safety-tested (they are), and that vaccines contribute to autism (they don’t).

“This is like the boy who cried wolf,” said Brian Lee, an epidemiologist at Drexel University. “One day he might be right about something and Americans who are not prone to conspiracies won’t trust it because it’s coming from RFK’s mouth. And that could be a problem.”

What’s more, the Trump administration is eroding scientists’ ability to probe the safety of pharmaceuticals, said Robert Steinbrook, head of health research at Public Citizen, a nonprofit consumer protection group.

“Public Citizen is very supportive of research on medications that could be linked to diseases,” he said. “But it needs to be through an open process, which looks at scientific evidence, and which doesn’t cherry-pick studies to support a preconceived point of view.”

Steinbrook said the administration has undermined his confidence in the government’s ability to conduct credible work. The Food and Drug Administration has held less than a third the number of advisory committee meetings this year as it did last, meaning fewer opportunities for experts to discuss research on the risks and benefits of drugs. The Trump administration has fired hundreds of career scientists at the CDC and FDA and cut millions of dollars in research funds, including to projects studying autism.

In early September, the CDC issued an unusual contract with the Rensselaer Polytechnic Institute to analyze datasets for signs that vaccinated children were more likely to have autism. Unlike with other research initiatives, the CDC didn’t post an open call for applications in advance. This allows agency experts to review proposals and select studies best designed to answer the question at hand.

CDC researchers told KFF Health News that experts in the agency’s autism and disability group weren’t aware of the contract or asked to review the proposal. That’s important, they said, because researchers digging through data to find clues about autism must show how they’ll rule out biological and environmental exposures that muddy the results, and ensure that children have been accurately diagnosed. One researcher said, “It absolutely looks like Kennedy has subverted the grantmaking process.”

The CDC and HHS did not respond to KFF Health News’ requests for information on the grant, including through a Freedom of Information Act request.

The new vaccine study is separate from Kennedy’s autism data-science initiative, which was posted as an open call at the National Institutes of Health. “The hope is that something good comes of it, and that the government won’t cherry-pick or censor what scientists find out,” Lee said.

Bauer said she didn’t apply to be part of the initiative because of Kennedy’s outsize presence at HHS.

“I would not take his funding because it could take away from the credibility of my study,” she said, “in the same way that taking money from pharmaceutical companies does.”