Recent studies challenge Kennedy’s claims about vaccines, Tylenol and antidepressants

These are important talking points for Health Secretary Robert F. Kennedy Jr. and his top officials: Taking Tylenol during pregnancy may be linked to autism. Antidepressants can be harmful during pregnancy. Aluminum salts present in vaccines may pose a health risk. And Covid vaccines do not benefit healthy children.

The remarks have caused confusion over the past year, with scientists warning there is no evidence to support them. Nonetheless, federal health agencies have pursued policies based on these claims.

Now, a series of new research published in recent months offers some of the strongest rebuttals yet.

The latest breakthrough came this month: After Food and Drug Administration officials questioned the safety of taking antidepressants during pregnancy, new research presented at an annual meeting of the Society for Maternal-Fetal Medicine found that pregnant patients who stopped taking their medications nearly doubled their risk of mental health-related emergency room visits.

Other recent studies have also shown that aluminum salts in vaccines are not linked to major safety concerns and that Covid shots have a protective effect for children.

Some documents were initiated in response to statements by Kennedy and the White House, while others were already in progress.

“These are just the latest examples in a decade-long record of Secretary Kennedy making claims about vaccines that are contradicted by facts and data,” Michael Osterholm, executive director of the Vaccine Integrity Project at the University of Minnesota, said in a statement. The project was launched after Kennedy’s confirmation to create an independent and transparent process for evaluating vaccine safety, he said.

Emily Hilliard, a spokesperson for the Department of Health and Human Services, said in a statement that “HHS remains focused on rigorous scientific review, transparency, and ensuring the continued safety and effectiveness of the U.S. vaccine supply.”

The Trump administration has pledged to conduct its own “gold standard” studies on vaccine safety and the causes of autism, among other topics of interest to Kennedy. But those studies haven’t been done yet — and many public health experts wonder whether they will be unbiased when they do. (Decades of studies have debunked the link between vaccines and autism.)

Already, some of the administration’s high-profile claims about drugs and vaccines have become the official positions of federal health agencies: The Centers for Disease Control and Prevention stopped recommending Covid shots for healthy children last year, and in September, with Kennedy behind him, President Donald Trump told pregnant women to “fight like hell” not to take Tylenol.

What is safe to take during pregnancy?

Over the past year, several top health officials have warned of the potential dangers of taking Tylenol and antidepressants during pregnancy. But the latest evidence published since January does not support these concerns.

The FDA convened a panel in July in which nearly all of the panelists raised concerns about pregnant women taking selective serotonin reuptake inhibitors — a class of antidepressants that includes Lexapro, Prozac and Zoloft. This stance went against the American College of Obstetricians and Gynecologists’ recommendation that pregnant patients continue to take their medications. Psychiatrists widely criticized the event.

FDA Commissioner Dr. Marty Makary said during the panel that SSRIs can cause birth defects and questioned their effectiveness, saying “the more antidepressants we prescribe, the more depression there is.” Some panelists also called for stronger warnings on SSRI drug labels.

Hilliard told NBC News that “the FDA will thoroughly review the data and update product labels as appropriate” if high-quality research reveals safety concerns beyond what is mentioned on the labels.

SSRI labels currently refer to a potential increased risk of excessive bleeding called postpartum hemorrhage in the mother or a life-threatening breathing problem called persistent pulmonary hypertension in the newborn. However, the data suggests that these risks are minimal, especially when compared to the risks of depression itself.

“In general, we don’t think it’s so risky that we would recommend a patient stop treatment because of it,” said Dr. Kelly Zafman, a maternal-fetal medicine researcher at the Hospital of the University of Pennsylvania.

Untreated depression alone can increase the risk of premature birth and preeclampsia. Scientists have also not found strong evidence that SSRIs are linked to autism or birth defects.

Zafman this month presented a new study analyzing the health insurance claims of nearly 4,000 patients with depression or anxiety who took antidepressants before their pregnancies. Among women who stopped taking antidepressants during pregnancy, 1,357 had emergency room visits related to mental health problems, compared to 795 who continued to take their prescriptions.

Zafman said some of the emergency room visits could be linked to overdoses, suicide attempts or debilitating insomnia, although insurance data does not specify the type of mental health emergency. Many of these problems can be life-threatening to the fetus.

A drug more commonly taken sometimes during pregnancy, Tylenol, also does not pose the dangers described by Trump and Kennedy.

Both men warned in September of a potential link between Tylenol during pregnancy and autism in children. Makary also asked doctors in a written advisory to “consider minimizing the use of acetaminophen,” the active ingredient in Tylenol.

Hilliard, the HHS spokesperson, said many experts have expressed concern about the use of acetaminophen during pregnancy. However, strong scientific evidence does not support this claim. Kenvue, the maker of Tylenol, said research shows acetaminophen does not cause autism, and it urged U.S. regulators not to put an autism warning label on the drug.

A group of researchers attempted to clear up the confusion last month by publishing one of the most in-depth analyzes on the subject. The team excluded studies with evidence of bias, such as those that did not follow study participants for very long or did not disclose the health histories of pregnant women. They found no link between acetaminophen use during pregnancy and neurodevelopmental disorders, including autism.

“We know that autism is this complex interaction between hundreds of genes and environmental factors early in pregnancy,” said Dr. Peter Hotez, dean of the National School of Tropical Medicine at Baylor College of Medicine in Texas and co-director of the Texas Children’s Hospital Center for Vaccine Development.

Certain chemical exposures early in pregnancy may interact with autism genes, Hotez said, but Kennedy “has no interest in actually evaluating them.”

Vaccines: supposed risks and demonstrated benefits

In September, the CDC officially changed its Covid vaccine guidelines to recommend that people decide with their doctor whether to get vaccinated. A few months earlier, Kennedy, Makary and Dr. Jay Bhattacharya, director of the National Institutes of Health, said the agency would no longer recommend Covid shots for healthy children and pregnant women.

In a video on X announcing the change, officials claimed there was no evidence supporting giving Covid boosters to children. The FDA’s top vaccine regulator, Dr. Vinay Prasad, also told staffers in a memo last fall that Covid shots had killed at least 10 children — but did not provide evidence, such as documentation of the deaths, to support that claim.

The CDC’s own research has consistently found that Covid vaccines and boosters protect against serious illness in children. More recently, a CDC study in December found that Covid vaccines administered from 2024 to 2025 reduced the risk of Covid-related emergency room and urgent care visits by 76% among children aged 9 months to 4 years and by 56% among children aged 5 to 17 years.

Kennedy, who has a history of anti-vaccine activism, called the Covid vaccine in 2021 “the deadliest vaccine ever made.” In June, he fired former members of the CDC’s vaccine advisory committee and replaced them with a group largely skeptical of Covid shots.

Under his leadership, HHS is studying whether aluminum salts in vaccines could be linked to autism, according to a statement posted on the CDC website in November. Trump said at a news conference last year that aluminum was being “taken out of vaccines,” adding, “Who the hell wants that injected into a body?”

Aluminum salts – which occur naturally in soil and water – are added to vaccines to boost the body’s immune response, allowing a lower dose to be used. Nearly a century of evidence has shown them to be safe for this purpose. In the United States, many childhood vaccines contain aluminum salts, including those for hepatitis A and B, HPV, meningitis, and whooping cough.

However, aluminum salts have been the target of many anti-vaccine activists. Kennedy told food blogger Mikhaila Peterson in 2021 that the brains of children with autism are “loaded with aluminum.”

A December analysis in the journal Pediatrics examined existing evidence in light of growing vaccine hesitancy. Researchers have not detected any major safety concerns related to aluminum salts in vaccines.

“That’s kind of Kennedy’s playbook. He never followed the science,” Hotez said. “You can throw all the evidence you want at him and he doesn’t realize it. It’s about choosing what he thinks supports his agenda.”