A Centers for Disease Control and Prevention webpage that once stated unequivocally that vaccines do not cause autism has been rewritten, now suggesting without evidence that health authorities “ignored” possible links between the shots and autism.
“The claim ‘vaccines do not cause autism’ is not an evidence-based claim because studies have not ruled out the possibility that infant vaccines cause autism,” the new language states. The change was posted Wednesday and first reported by The Wall Street Journal.
Pediatricians and vaccine experts have long said that autism is among the most studied childhood conditions and that no credible research has ever suggested a link between it and vaccines.
The messaging is an about-face to the agency’s decades of research showing that any link between vaccines and autism has been scrutinized time and time again and thoroughly debunked.
Scientists, vaccinologists and autism researchers who’ve sought to identify possible causes were gobsmacked by the change.
“This is madness,” Dr. Sean O’Leary, head of the American Academy of Pediatrics’ infectious diseases committee, said during a media briefing Thursday. O’Leary said that scientists have taken an exhaustive look at potential environmental causes of autism. “One thing that is very clear is that vaccines are not one of those things. They do not cause autism. Period.”
The Autism Science Foundation said in a statement that the group is “appalled” by the change in CDC messaging, calling it “anti-vaccine rhetoric and outright lies about vaccines and autism.”
“The idea that vaccines cause autism is not only scientifically false,” ASF director Alison Singer said during a media briefing, “it’s also profoundly stigmatizing to autistic people and to their families. It frames autism as being caused by parental action, as if autism is a preventable injury.”
Still, the updated webpage also notes that the Department of Health and Human Services has launched “a comprehensive assessment” to examine the causes of autism. It’s unclear what the assessment will be or how it will be conducted.
HHS spokesman Andrew Nixon said the website had been updated “to reflect gold standard, evidence-based science.” A question about how the agency defines such science wasn’t immediately answered.
The new language comes just ahead of the CDC’s vaccine advisory committee meeting scheduled for Dec. 4-5, where members are expected to vote on changing the childhood schedule for hepatitis B vaccines. When the Advisory Committee on Immunization Practices met in September, the panel delayed changing the guidance that all newborns should be vaccinated against the incurable infection.
The Trump administration had previously demanded changes to the CDC website, notably insisting that anything related to diversity, equity and inclusion, or DEI, be erased.
This latest revision “crossed the line,” said Dr. Jesse Goodman, an infectious disease specialist at Georgetown University Medical Center and former chief scientist with the Food and Drug Administration.
The administration has “hijacked the premiere public health industry to pursue a narrow agenda of spreading inaccurate information about vaccines,” Goodman said.
The new CDC messaging wasn’t reflected across the agency’s website, however. A page for parents states that “scientific studies and reviews continue to show no relationship between vaccines and autism.”
Still, the revision was the clearest signal yet that the CDC may no longer be a source for objective scientific findings and advice.
“In my deepest heart, this is the day CDC died,” said a former CDC official who asked not to be named for safety reasons. “The public won’t care about nuance and individual websites now. Any messaging trying to distinguish some from all will sound tone deaf.”
Changes on the CDC page seemed to contradict a commitment Health Secretary Robert F. Kennedy Jr. made to Sen. Bill Cassidy of Louisiana, a Republican, during Kennedy’s confirmation hearing earlier this year.
During the hearing, Cassidy told Kennedy, “My concern is that if there is any false note, any undermining of a mama’s trust in vaccines, another person will die from a vaccine-preventable disease.” After getting assurances from Kennedy not to undermine faith in vaccines, Cassidy voted to confirm him.
A key section on the page kept the heading, “Vaccines do not cause Autism,” but with an asterisk added. Following that is a newly added asterisk noting the heading is there “due to an agreement with the chair of the U.S. Senate Health, Education, Labor, and Pensions Committee that it would remain on the CDC website.”
One CDC staffer not permitted to speak to the media said they read the Cassidy reference as “a direct middle finger” to the senator.
Cassidy didn’t respond to a request for comment. He later posted on X that “vaccines for measles, polio, hepatitis B and other childhood diseases are safe and effective and will not cause autism. Any statement to the contrary is wrong, irresponsible, and actively makes Americans sicker.”
Kennedy has long been known as an anti-vaccine activist.
Dr. Amesh Adalja, an infectious disease physician and senior scholar at Johns Hopkins Center for Health Security, said the update to the CDC webpage is a nod to anti-vaccine activists that Kennedy hasn’t forgotten them.
“He’s signaling to his tribe that he’s there and he’s doing their bidding,” Adalja said.
What do the autism studies really show?
Some scientists and doctors accused the CDC of cherry-picking studies that raise doubt about the relationship between autism and vaccines, and misrepresenting data or omitting credible studies that don’t show an association.
“They’re taking evidence of safety and pretending it shows uncertainty. And I think that’s in a lot of ways actually worse than citing bad studies, because it’s corrupting good ones,” said Dr. Jake Scott, an infectious diseases specialist at Stanford Medicine.
For instance, the CDC webpage points to a large Danish study from July, which found that aluminum exposure from vaccines during the first two years of life was not associated with increased rates of neurodevelopmental disorders. The study looked at more than 1.2 million children over roughly two decades and is considered one of the most robust pieces of evidence that vaccines and autism aren’t linked.
“If aluminum in vaccines were causing autism or other chronic conditions, that study would have found it,” Scott said. “But ironically, they actually found slightly lower rates of autism with higher aluminum exposure.”
However, the CDC webpage highlights a supplementary figure in the study suggesting an increased risk of Asperger’s syndrome in a tiny subset of children. Scott described the result as a “statistical blip.”
“When you test 50 different conditions, you expect to see a couple of outliers just by pure chance. That’s just basic statistics,” he said.
The webpage also cites two reports from the Institute of Medicine (now known as the National Academy of Medicine) — from 1991 and 2012 — suggesting there wasn’t enough data to say whether the pertussis vaccine causes autism.
“Those reports actually rejected links between vaccines and autism,” Scott said.
Other studies cited on the CDC webpage that cast doubt on the safety of vaccines aren’t well conducted, he added.
The CDC references a 2014 study suggesting that aluminum in vaccines given to infants may be associated with a rise in autism cases. Scott said the study merely showed that two things happened at the same time — autism cases rose and the number of aluminum-containing vaccines given to children went up — not that they’re connected.
“The classic analogy is like saying ice cream sales cause drowning, because both increase in the summertime,” he said.
The CDC webpage also points to a 2010 study, which suggested that boys vaccinated for hepatitis B as newborns had a threefold higher risk of autism compared with boys who were vaccinated later or never vaccinated. The study was based on parent surveys rather than medical records. Studies using medical records have found no link, Scott said.
“They’re not mentioning the dozens of other studies that have failed to show an association,” Alycia Halladay, chief science officer at the Autism Science Foundation, said of the CDC’s updated webpage.
One study that’s “blatantly missing,” she said, is a 2015 analysis that considered the hereditary nature of autism. The researchers found that the measles, mumps and rubella (MMR) vaccine was not associated with increased risk of autism, even among children with a higher risk of the disorder because their older siblings had it. A massive review in 2021, which evaluated 138 studies, also found that MMR vaccines don’t cause autism, but was not cited on the CDC webpage.
The bulk of research cements any doubt for ASF’s Alison Singer.
“At some point you have to say that this question is asked and answered, just like we no longer study whether the Earth is flat or round,” she said. “Enough is enough.”