That taking Tylenol during pregnancy may be linked to autism. That antidepressants can be harmful to pregnant women and their babies. That aluminum salts in vaccines can pose a health risk. Or that COVID-19 vaccines do not benefit healthy children.
All are central themes in the speech of the Secretary of Health of the United States, Robert F. Kennedy Jr., and other senior health officials under his command.
These claims have sown confusion over the past year. And although the scientific community warns that there is no evidence to support them, federal health agencies have implemented measures and policies based on them.
But new research published in recent months represents the most forceful refutation to date of the Health Secretary’s claims.
The most recent discovery occurred this month. After Food and Drug Administration officials questioned the safety of antidepressants during pregnancy, new research presented at the annual meeting of the Society for Maternal-Fetal Medicine found that pregnant patients who stopped taking those medications had nearly double the risk of going to the emergency room for mental health problems.
Other recent studies have also found that aluminum salts in vaccines are not linked to relevant safety issues and that COVID-19 immunizations have a protective effect for children.
Some research and scientific articles were launched in response to statements from Kennedy and the White House, while others were already in the works earlier.
“These are just the latest examples in a decade-long list of statements by Secretary Kennedy about vaccines that contradict facts and data,” Michael Osterholm, executive director of the Vaccine Integrity Project at the University of Minnesota, said in a statement. The project began operating after Kennedy’s confirmation in Congress, to create an independent and transparent process for evaluating the safety of vaccines, Osterholm explained.
Emily Hilliard, spokesperson for the Department of Health and Human Services (HHS), said in a statement that “HHS remains focused on rigorous scientific review, transparency, and ensuring the continued safety and effectiveness of the vaccine supply in the United States.”
Donald Trump’s administration has committed to conducting its own “baseline” studies on the safety of vaccines and the causes of autism, among other topics of interest to Kennedy. But those analyzes have not yet been done, and many public health experts wonder whether they will be free of bias when they are done. Decades of studies have disproved the relationship between vaccines and autism.
Some of the Administration’s most notable claims about drugs and vaccines have already become the official position of federal health agencies: The Centers for Disease Control and Prevention (CDC) stopped recommending COVID-19 vaccines for healthy children last year, and in September, with Kennedy’s blessing, the president told pregnant women to “fight tooth and nail” to avoid taking Tylenol.
What drugs are safe during pregnancy?
In the last year, several top health officials have warned about the possible harms of taking Tylenol and antidepressants during pregnancy. However, the most recent evidence released since January does not support those concerns.
The FDA convened a panel in July in which nearly all panelists expressed concerns about pregnant women’s use of 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 taking the medications. Psychiatrists widely criticized the event.
FDA Commissioner Dr. Marty Makary stated during the panel that SSRIs can cause birth defects and questioned their effectiveness, claiming that “the more antidepressants we prescribe, the more depression there is.” Some panelists also called for more severe warnings to be included on SSRI drug labels.
Hilliard told NBC News that “the FDA will carefully review the data and update product labels as appropriate” if high-quality research shows safety issues beyond what is listed on the labels.
Labels for SSRIs currently refer to a possible increased risk of excessive bleeding, known as postpartum hemorrhage in the mother, or to a life-threatening breathing problem called persistent pulmonary hypertension in the newborn. However, evidence suggests that these risks are minimal, especially compared to the risks of depression itself.
“Overall, we don’t think it’s risky enough to recommend that a patient stop taking her medication because of it,” said Dr. Kelly Zafman, a maternal-fetal medicine specialist at the Hospital of the University of Pennsylvania.
By itself, untreated depression can raise the risk of preterm birth and preeclampsia. Scientists have also found no strong evidence that SSRIs are linked to autism or birth defects.
Zafman presented new research this month that analyzed the health insurance claims of nearly 4,000 patients with depression or anxiety who took antidepressants before becoming pregnant. Among women who stopped taking antidepressants during pregnancy, 1,357 went to the emergency room for mental health problems, compared with 795 who continued taking the medication.
Zafman added that some of the ER visits could be related to overdoses, suicide attempts or debilitating insomnia, although the insurance data did not specify the type of mental health emergency. Many of these problems can endanger the life of the fetus.
A more common medication sometimes taken during pregnancy, Tylenol, also does not carry the dangers that Trump and Kennedy have described.
In September, both warned of a possible link between Tylenol use during pregnancy and autism in children. Makary also recommended doctors in a written statement “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, there is no solid scientific evidence to support this claim. Kenvue, maker of Tylenol, has stated that research shows that acetaminophen does not cause autism, and has urged US regulators not to include a warning about autism in the drug’s package insert.
A group of researchers attempted to clear up the confusion last month by publishing one of the most comprehensive analyzes on the topic. The team excluded studies with evidence of bias, such as those that did not follow participants for a long time or did not reveal the medical history of pregnant women. They found no relationship between acetaminophen use during pregnancy and neurodevelopmental disorders, including autism.
“We know that autism is a complex interaction between hundreds of genes and environmental factors in early 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 Center for Vaccine Development at Texas Children’s Hospital.
Certain chemical exposures in early pregnancy may interact with autism genes, Hotez added, but Kennedy “has no interest in testing them.”
Vaccines: supposed risks and demonstrated benefits
In September, the CDC formally changed its guidance on COVID-19 vaccines to recommend that people decide with their doctors whether to get vaccinated. Months earlier, Kennedy, Makary and Dr. Jay Bhattacharya, director of the National Institutes of Health, said the agency would no longer recommend COVID-19 vaccines for healthy children and pregnant women.
In an X video announcing the change, officials said there was no evidence to support giving COVID-19 booster doses to children. The FDA’s top vaccine regulator, Dr. Vinay Prasad, also told staff in a memo last fall that COVID-19 vaccines had killed at least 10 children, but provided no evidence, such as documentation of the deaths, to support that claim.
CDC’s own research has consistently shown that COVID-19 vaccines and booster doses protect against severe disease in children. More recently, an agency study conducted in December found that coronavirus vaccines administered between 2024 and 2025 reduced the risk of emergency room visits and urgent medical care by 76% among children ages 9 months to 4 years and by 56% among children ages 5 to 17.
Kennedy, who has a history of anti-vaccine activism, called the 2021 COVID-19 immunization “the deadliest ever made.” In June, he fired the previous members of the CDC’s vaccine advisory committee and replaced them with a group largely skeptical of vaccines.
Under his leadership, HHS is investigating whether aluminum salts in vaccines could be linked to autism, according to a statement posted on the CDC website in November. Trump added in a press conference last year that aluminum was being “removed from vaccines,” adding, “Who the hell wants that stuff injected into their body?”
Aluminum salts, which are naturally present in soil and water, are added to vaccines to enhance the body’s immune response, allowing a lower dose to be used. Nearly a century of testing has shown them to be safe for that purpose. Many childhood vaccines in the United States 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 assured food blogger Mikhaila Peterson in 2021 that the brains of children with autism were “loaded with aluminum.”
An analysis published in December in the journal Pediatrics reviewed existing evidence in light of growing vaccine hesitancy. The researchers did not detect any major safety concerns related to aluminum salts in the vaccines.
“This is Kennedy’s usual strategy. He has never followed science,” Hotez said. “You can present him with all the evidence you want and he will ignore it. He just cherry-picks what he thinks supports his agenda.”
