By Maryanne Demasi at Brownstone dot org.
For the first time in a generation, the US Centers for Disease Control and Prevention (CDC) has rewritten its official position on whether vaccines can cause autism.
This is a change that could reshape one of the most politically charged and emotionally fraught debates in modern medicine.
In a website update published on 19 November 2025, the agency now states that the long-standing claim "vaccines do not cause autism" is "not an evidence-based claim" because scientific studies "have not ruled out the possibility that infant vaccines cause autism."
The page also acknowledges that "studies supporting a link have been ignored by health authorities."
It's difficult to overstate the significance of these statements. For nearly two decades, they would have been unthinkable for a federal public health agency.
The timing is equally striking.
The change arrives at a moment when the political and scientific landscape around vaccine safety is undergoing a marked shift inside the Trump–Kennedy administration.
For months, critics have accused Health Secretary Robert F. Kennedy Jr and several of the administration's appointees of holding unconventional views on vaccine safety.
The CDC's revised language now places the agency closer to Kennedy's long-standing argument that federal agencies had ignored crucial evidence.
The CDC explains the shift by pointing to the Data Quality Act, which requires federal communications to accurately reflect the evidence.
Because studies have not excluded the possibility that infant vaccines could contribute to autism, the agency concedes that its long-standing categorical statement was not scientifically justified.
The update states plainly that scientific uncertainty remains, particularly for vaccines administered in the first year of life.
Scientific Uncertainty Finally Acknowledged
The information on the website draws a sharp distinction between the infant vaccine schedule — which includes DTaP, HepB, Hib, IPV, PCV and others — and the measles–mumps–rubella (MMR) vaccine.
For the MMR, the CDC continues to cite observational evidence showing "no association … with autism spectrum disorders," describing the conclusion as supported by "high strength of evidence."
But the agency also acknowledges that these studies had "serious methodological limitations" and were all retrospective epidemiological analyses, the type that cannot establish cause and effect or identify subgroups who may be more vulnerable.
The acknowledgement of limitations is unusually candid for a federal agency discussing vaccines and autism.
For the infant vaccine schedule, the shift is even more dramatic.
The CDC cites a series of authoritative reviews — including the 1991 and 2012 Institute of Medicine's assessments, and the Agency for Healthcare Research and Quality's review in 2021 — all concluding that the evidence was "inadequate to accept or reject" a causal relationship between early-life vaccines and autism.
In other words, the fundamental scientific question remains unresolved.
Political Dynamite
The political context makes this change even more consequential. Senator Bill Cassidy (R-LA), who chairs the Senate Health Committee, has been one of the most vocal critics of Kennedy's vaccine views.
Cassidy has repeatedly insisted that the science on autism and vaccination was settled years ago. Now the CDC states that the claim "vaccines do not cause autism" does not meet evidence standards.
Remarkably, the CDC states that the headline phrase remains on the page only "due to an agreement with the chair of the U.S. Senate Health, Education, Labor, and Pensions Committee."
The implication — that the wording is a political compromise rather than a scientific one — will undoubtedly invite scrutiny on Capitol Hill.
Attorney Aaron Siri, who has spent years litigating against federal agencies for greater transparency around vaccine safety, said the update marks a long-overdue shift in honesty from...