Opinion: Vaccines don’t cause autism. The CDC should say so.

On Nov. 20, the Centers for Disease Control and Prevention (CDC) released an updated webpage on “Autism and Vaccines” suggesting that autism is linked to and caused by infant vaccines. As San Diego scientists and clinicians who work directly with children with autism and their families at San Diego State University and UC San Diego, we were alarmed. The CDC’s new wording is misleading, scientifically unfounded and dangerous, especially for communities like ours already grappling with declining vaccination rates and rising preventable illnesses.

The CDC now states that “scientific studies have not ruled out the possibility that infant vaccines contribute to the development of autism.” This statement implies uncertainty where none exists. In reality, decades of rigorous research conducted in the United States and around the world have consistently and conclusively found no link between vaccines and autism. In fact, the evidence on this question is among the most consistent in all of public health: Vaccines do not cause autism.

One example illustrates the scale and quality of the evidence. A landmark study in Denmark, published in the New England Journal of Medicine, followed more than 537,000 children, nearly the entire birth cohort of the country over several years. The study found that autism rates were identical in vaccinated and unvaccinated children, regardless of age at vaccination, time since vaccination, or dosing schedule. Researchers in multiple countries have replicated this finding again and again, using different populations, methodologies and data sources.

Against this overwhelming evidence, the CDC chose to cite two long-discredited papers by Mark and David Geier, studies rejected years ago for severe methodological flaws. One of the authors lost his medical license; the other was convicted for practicing without one and for endangering children with autism through unproven and harmful treatments (a hormone-suppressing drug Lupron). Presenting their work as credible is not merely careless. It is scientifically irresponsible.

Equally troubling is the CDC’s use of parental belief as evidence. The agency cites a small study of 150 families from two clinics in New York, half of whom did not respond to the survey, to suggest that some parents think vaccines triggered their child’s autism. But belief is not data. It reflects the emotional complexity parents face when navigating a diagnosis, not scientific causation. Relying on such anecdotal perceptions to inform national health guidance is inappropriate and misleading.

The CDC’s miscommunication is particularly harmful here in San Diego, where erosion of trust in vaccines has already had measurable effects. In the 2023–2024 school year, only 94.8% of San Diego County kindergarteners received the MMR vaccine, below the 95% herd-immunity threshold needed to prevent outbreaks. Many individual schools fall even further below that line.

This drop is not theoretical. It has consequences. In 2024, San Diego County reported 547 cases of pertussis (whooping cough), a sharp increase from 332 the previous year. Infants who are too young to be fully vaccinated face the highest risk of hospitalization and complications. Local pediatricians have also treated cases of measles and other diseases that were once nearly eliminated. When national health agencies cast doubt, even implicitly, on vaccine safety, they amplify these threats. The result will be more outbreaks, more hospitalizations, and more preventable deaths — especially among infants and immunocompromised children.

It is worth noting that San Diego County’s own Immunization Unit clearly states that vaccines are not linked to autism. Our local public health experts continue to provide clear, evidence-based communication. The CDC should be modeling that leadership, not undermining it.

There is another cost: reviving the false narrative that vaccines cause autism harms people with autism by diverting attention from efforts to support children and adults with autism in schools, clinics and workplaces. Autism is a neurodevelopmental condition, not the consequence of vaccines or parental choices.

As San Diego autism scientists and clinicians, we care deeply about accuracy in public health communication. Families in our region trust institutions like the CDC to provide clear, evidence-based information. In this case, the agency has failed to do so. The CDC’s November statement contradicts the established consensus, relies on discredited studies and misrepresents weak anecdotal perceptions as evidence. It undermines public confidence and jeopardizes community health at a time when clarity and trust are more important than ever.

We urge the CDC to correct its misleading statement and reaffirm what decades of rigorous research have already shown: Vaccines do not cause autism. San Diego families deserve guidance rooted in scientific evidence, not messaging that sows confusion and fear.

Fishman, Ph.D., is a clinical neuropsychologist at San Diego State University. Carver, Ph.D., is a developmental psychologist at UC San Diego. Akshoomoff, Ph.D., is a clinical neuropsychologist at UC San Diego.