U.S. President Donald Trump on Monday linked autism to childhood vaccines and also to the use of popular pain medication Tylenol for pregnant women and children, claims which are not backed by decades of science.

In an extraordinary news conference at the White House, the Republican president delivered medical advice to pregnant women and parents of young children, repeatedly telling them not to use or administer the over-the-counter pain killer.

The advice from Trump, who has no medical training and also pointed out “I’m not a doctor,” goes against that of medical societies, which cite data from numerous studies showing acetaminophen plays a safe role in the well-being of pregnant women.

“I want to say it like it is, don’t take Tylenol. Don’t take it,” Trump said. “Fight like hell not to take it. There may be a point where you have to, and that you’ll have to work out with yourself, so don’t take Tylenol.”

Standing next to Health Secretary Robert F. Kennedy Jr., a vaccine critic who has argued that no vaccine is safe, Trump called for a reexamination of a link between vaccines and autism, a theory that has been repeatedly debunked, and a series of changes not grounded in science.

“We believe independent, sound science clearly shows that taking acetaminophen does not cause autism. We strongly disagree with any suggestion otherwise and are deeply concerned with the health risk this poses for expecting mothers,” Kenvue, the maker of Tylenol, said in a statement ahead of the announcement.

Shares of Kenvue slid more than 7 per cent during Monday’s stock market session as investors braced for Trump’s announcement. But the shares recovered 5 per cent in extended trade.

Trump said he is a big believer in vaccines, having led in his first-term the pandemic initiative to speed COVID-19 vaccine development. Still, he called for the removal of mercury from vaccines and said children should not get the hepatitis B vaccine before the age of 12. It is given in the first 24 hours after birth. He also said the measles-mumps-rubella combination vaccine should be split into three separate vaccines.

The announcement was reminiscent of Trump’s regular press briefings in the early months of the pandemic when he would frequently dispense advice that was not founded on science, including his suggestion that people drink bleach, which his supporters later said was not serious.

Studies have shown vaccines are safe and have saved millions of lives, eradicating childhood diseases such as polio and measles in the U.S.

Over the last 50 years, it is estimated that essential vaccines have saved at least 154 million lives, UNICEF USA President & CEO Michael J. Nyenhuis has said.

Only one in four Americans believe recent recommendations for fewer vaccines from the Trump administration were based on scientific evidence and facts, a Reuters/Ipsos poll showed this month.

“I cannot say that I’ve ever experienced anything like this in vaccines,” said Dr. Norman Baylor, former director of the FDA’s Office of Vaccines Research and Review.

Trump administration announces steps it will take

The Trump Administration also suggested leucovorin, a form of folic acid, as a treatment for autism symptoms.

The Food and Drug Administration approved a version of the drug made by GSK it had previously withdrawn for a condition it associated with autism. Once it is established for the use, the administration said, Medicaid insurance for low-income people would cover the drug for autism symptoms.

The FDA, in its approval, cited a review of the use of leucovorin in 40 patients with a rare metabolic disorder called cerebral folate deficiency that can lead to a range of neurological symptoms, some of which are seen in people with autism.

The FDA will notify doctors that using Tylenol during pregnancy can be associated with a very increased risk of autism, Trump said, without presenting evidence for the claim.

The Trump administration said it plans to initiate a change to the safety label on Tylenol, which would say that research shows it can lead to adverse neurological outcomes.

Researchers say there is no firm evidence of a link between the use of Tylenol and autism. A 2024 study of nearly 2.5 million children in Sweden found no causal link between in utero exposure to acetaminophen and neurodevelopmental disorders.

A 2025 review of 46 earlier studies did suggest a link between prenatal acetaminophen exposure and increased risks of these conditions, but the researchers from the Icahn School of Medicine at Mount Sinai, Harvard University and others said the study does not prove the drug caused the outcomes. They advised that pregnant women should continue to use acetaminophen as needed, at the lowest possible dose and for the shortest possible period.

Tylenol is made by consumer health company Kenvue, which was spun off from Johnson & Johnson in 2023, and generic versions of acetaminophen are also available. The company said on Monday it disagreed with the suggestion of a link which it said was not based in science.

Researchers say leucovorin, used to treat some cancer patients on chemotherapy, has shown some promise in very small trials, but that large, randomized trials are still needed.