For those who follow medical misinformation, the claim that childhood vaccines cause autism is the ultimate warning sign. This topic is one of the most heavily researched in modern science, and the conclusion has been unwavering: There is no link.
That is why the Centers for Disease Control and Prevention’s recent revision to its vaccine–autism guidance landed with such force—and not in a positive way. Previously, the CDC’s statement read:
“Studies have shown that there is no link between receiving vaccines and developing autism spectrum disorder… No links have been found between any vaccine ingredients and ASD.”
However, as of last week, the page now states: “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.”
This change didn’t appear out of nowhere. Health and Human Services Secretary Robert F. Kennedy Jr. has hinted for months that he intends to reopen the debate about autism’s origins. The CDC’s updated language is simply the clearest indication yet that his broader campaign against childhood immunization is beginning to erode long-established public health science.
And the implications go far beyond one webpage.
I’ve been covering Kennedy’s assault on public health since his name was first floated as a potential cabinet nominee in a second Trump administration. After taking office, Kennedy removed all 17 public members of the CDC’s prestigious Advisory Committee on Immunization Practices, replacing seasoned physicians and vaccine specialists with known antivaccine activists and individuals with little or no scientific background.
The result was predictable: The committee’s first meeting under its new leadership was marked by confusion, misinformation, and a lack of basic scientific understanding.
Kennedy also appointed a supporter of the debunked vaccine–autism theory to lead a study on the supposed connection. He and Trump have made repeated attempts to link autism to maternal Tylenol use during pregnancy and even to circumcision—claims entirely unsupported by credible evidence.
At his first press conference in April, Kennedy made a series of false statements about autism. He described it as a rampant “epidemic,” which it is not, and claimed “most cases now are severe,” which is also untrue. In reality, the majority of new diagnoses involve children without the intellectual disabilities historically associated with autism. A Rutgers study even found that severe cases have declined in recent years.
Kennedy frequently cites the rising number of autism diagnoses as proof of an “epidemic,” blaming childhood vaccines as a key driver. Yet extensive research has clarified autism’s root causes. Genetic variations are now understood to play a significant role, while vaccines have been definitively ruled out.
Part of the increase in diagnoses stems from the expanding definition of autism, now recognized as a wide-ranging spectrum of conditions. Still, Kennedy continues to villainize routine childhood vaccination.
The CDC’s revised webpage echoes Kennedy’s pseudoscientific approach, recycling rhetoric long used by antivaccine activists. The claim that “studies have not ruled out” a vaccine–autism connection is a distortion of scientific reasoning.
Science is not designed to prove a negative. As critics often note, there is no proof that drinking soda or eating pizza doesn’t cause autism either.
More importantly, Kennedy disregards the vast body of research on vaccines and autism—studies involving more than two million children worldwide, all showing no link. Instead, the CDC now cites a much weaker source: a small 2006 survey of 150 parents at two private clinics, of whom only 77 responded. Fifty-four percent of those respondents blamed vaccines for their child’s autism.
But as John Harrington, the study’s lead author, told me, “It’s just about parents’ views, not the science of autism.” The study itself clearly states that its purpose was to document beliefs, not validate them.
I asked Kennedy’s agency to explain why this outdated, non-scientific paper was now being presented as evidence. I received no response.
The consequences of the CDC’s shift are far-reaching. The most immediate concern is that more parents will reject vaccines. We already see the fallout from growing vaccine hesitancy fueled by Kennedy and other antivaccine influencers: Measles cases in the U.S. reached 1,753 as of Nov. 18, the highest number since 1991. Other preventable diseases, such as whooping cough, are also resurging.
The next casualty is the CDC’s reputation. Once one of the world’s most trusted public health institutions, it has devolved under Kennedy’s direction into what vaccinologist Paul Offit described as a “propaganda machine for RFK Jr.’s fixed, immutable, science-resistant theories.” If the agency is being used to promote antivaccine ideology, he asked, why should anyone trust it?
Collateral damage includes Sen. Bill Cassidy (R-La.), whose vote was crucial in confirming Kennedy as HHS secretary. Cassidy, a physician, initially doubted Kennedy’s qualifications but ultimately supported him after Kennedy promised not to interfere with the vaccine advisory committee. That promise was broken almost immediately.
Kennedy also pledged that the CDC would not remove statements affirming that vaccines do not cause autism. Technically, that phrase remains on the website—but now it sits beside an asterisk explaining that the wording is still there solely because of Kennedy’s agreement with Cassidy. It reads almost like an intentional jab.
Cassidy has not directly addressed this apparent slight. When asked on CNN, Jake Tapper stated bluntly: “Dr. Cassidy, he lied to you.” Cassidy sidestepped the accusation, reiterating that vaccines are safe and accusing Tapper of trying to provoke a partisan dispute.
Although Cassidy posted on social media reaffirming that childhood vaccines do not cause autism, he avoided mentioning Kennedy or the CDC’s changes. His office did not respond to questions about whether he would call for Kennedy’s resignation.
So long as Kennedy remains at the helm of the Department of Health and Human Services, the integrity of American public health is in jeopardy. The nation’s health agencies face unprecedented challenges, and the public—misled by disinformation and pseudoscience—will ultimately bear the cost.
