The US CDC updates its stance on vaccines and autism, sparking a dispute with the WHO and renewed debate over vaccine safety amid increasing autism diagnoses and political tensions.
A US government website now says it is no longer evidence-based to state flatly that vaccines do not cause autism, putting the Centers for Disease Control and Prevention on a collision course with the World Health Organization and much of the published research on vaccine safety. The CDC page, updated on 22 July 2026, says the claim “vaccines do not cause autism” should be withdrawn because studies have not ruled out the possibility that infant vaccines contribute to autism, and says the Department of Health and Human Services has begun a new review of possible causes.
That position is markedly at odds with the WHO’s latest assessment. In a statement issued on 11 December 2025, the agency’s Global Advisory Committee on Vaccine Safety said it had reviewed evidence published from January 2010 to August 2025 and again found no causal relationship between vaccines and autism spectrum disorder. The committee said 31 primary studies and five meta-analyses were examined, and that the strongest papers, drawn from 11 countries, did not support an association. It also said two papers suggesting a link with cumulative aluminium exposure were ecological studies, meaning they could not establish cause and effect, and were judged to be at critical risk of bias.
The dispute goes to the heart of Robert F. Kennedy Jr.’s long-running argument with mainstream public-health bodies. During his Senate confirmation hearing in January 2025, Bill Cassidy, the Louisiana Republican who is also a doctor, asked Kennedy to reassure parents “unequivocally and without qualification” that measles and hepatitis B vaccines do not cause autism. Kennedy would not do so. Instead, according to the Associated Press, he replied: “If the data is there, I will absolutely do that.” Bernie Sanders also pressed him on the point. AP reported that Kennedy similarly refused to accept the scientific consensus that Covid-19 vaccines saved millions of lives.
Cassidy’s concern was not abstract. According to AP’s account of the hearing, he warned Kennedy that “if there’s any false note, any undermining of a mama’s trust in vaccines, another person will die from a vaccine preventable disease”. Dr Sean O’Leary of the American Academy of Pediatrics told AP that Kennedy “ignores science” and “cherry-picks sometimes fraudulent studies”, and warned that weakening confidence in routine vaccination could bring back diseases that had become rare in children.
FactCheck.org’s review of the same exchange sheds light on the evidence Kennedy chose to rely on. Near the end of the hearing, Cassidy pointed him to a 2014 meta-analysis whose title, as Cassidy noted, was explicit: “Vaccines are not associated with autism: An evidence-based meta-analysis of case-control and cohort studies.” Kennedy answered by invoking a recently published paper involving 47,000 Florida Medicaid children and said it “shows the opposite”. FactCheck.org said the paper was funded by the National Vaccine Information Center, an anti-vaccine group, and that its authors lacked key information about which vaccines children received or whether some vaccinations took place outside the Medicaid system. The same article also revisited the 1998 Andrew Wakefield paper that ignited the modern vaccine-autism scare, noting that it was later found to be fraudulent and was retracted.
The CDC’s rewritten page sets out the government’s new rationale in unusually blunt terms. It says the earlier federal message that vaccines do not cause autism had been spread to prevent vaccine hesitancy, and argues that the question of infant vaccines has not been “properly and thoroughly studied”. The page contrasts the 1986 infant immunisation schedule, which it says involved five doses in the first year, with the far larger 2025 schedule, and says the rise in autism prevalence “correlates” with the growth in the number of infant vaccines, while acknowledging that correlation does not prove causation. It also leans on older Institute of Medicine and HHS reviews which found insufficient evidence to accept or reject a causal relationship for diphtheria-, tetanus- and pertussis-containing vaccines, rather than positive evidence of harm.
The politics around that argument were visible throughout Kennedy’s hearing. Maggie Hassan, the New Hampshire Democrat, spoke about decades of uncertainty over what caused her 36-year-old son’s cerebral palsy and said Kennedy’s suggestions were painful for families. On the Republican side, Tommy Tuberville said his granddaughter would not “be a pincushion” when it came to vaccines, while Markwayne Mullin objected to senators treating scepticism itself as improper, asking: “We can’t question science?” Tim Kaine, meanwhile, raised a separate conflict issue, saying Kennedy had made $850,000 in the previous year from arrangements tied to litigation over Gardasil. Kennedy replied that he had given away his rights in the case.
Once in office, Kennedy’s department made autism one of its most prominent policy themes. In a 22 September 2025 press release, HHS said autism had “surged nearly 400%” since 2000 and now affected 1 in 31 American children. The department announced 13 projects under the National Institutes of Health’s Autism Data Science Initiative, with total funding of more than $50 million. HHS said the programme would combine biological, clinical and behavioural data with an “exposomics” approach examining environmental, nutritional, medical and social factors alongside genetics.
What has changed since the January 2025 hearing is not the existence of a settled scientific literature abroad, but the posture of the US government itself. The WHO says decades of high-quality evidence, including the latest multinational reviews and a Danish registry study covering children born from 1997 to 2018, do not show a causal link. The CDC now says the opposite cannot be stated with confidence, and that federal research should revisit the question. That leaves parents, doctors and public-health officials confronting two sharply different messages from institutions that used to speak with far less daylight between them.
Disclaimer: This content is for informational purposes only and is not intended to be a substitute for professional medical judgment, advice, diagnosis, or treatment.
