Vaccines and Autism: What the Science Really Says

The CDC recently updated its webpage on autism and vaccines, suggesting a possible link between the two. This change has raised concerns, especially in places like San Diego, where vaccination rates are already dropping and preventable diseases are on the rise. The CDC's new wording is problematic because it implies that there is still uncertainty about whether vaccines cause autism. However, decades of research have consistently shown that there is no link between vaccines and autism. One major study in Denmark followed over 537, 000 children and found that autism rates were the same in vaccinated and unvaccinated kids. This study, along with many others, has repeatedly shown that vaccines do not cause autism. Despite this overwhelming evidence, the CDC cited two old and discredited studies by Mark and David Geier. These studies were rejected long ago because of serious flaws. One of the authors even lost his medical license, and the other was convicted for harming children with autism through unproven treatments. Using these studies as evidence is not just careless; it's scientifically irresponsible. The CDC also relied on a small survey of 150 families to suggest that some parents believe vaccines triggered their child's autism. But beliefs are not the same as scientific evidence. Parents may have many emotions when dealing with an autism diagnosis, but that doesn't mean vaccines are to blame. Using such weak and anecdotal information to guide national health policies is misleading and inappropriate. In San Diego, the drop in vaccination rates has real consequences. Only 94. 8% of kindergarteners in the 2023-2024 school year received the MMR vaccine, which is below the 95% threshold needed to prevent outbreaks. This has led to a sharp increase in cases of pertussis, or whooping cough, and even measles, which was once nearly eliminated. When national health agencies cast doubt on vaccine safety, even indirectly, they make these threats worse. The result is more outbreaks, more hospitalizations, and more preventable deaths, especially among infants and immunocompromised children. San Diego County's own Immunization Unit clearly states that vaccines are not linked to autism. Local public health experts continue to provide clear, evidence-based information. The CDC should be following their lead, not undermining it. The false narrative that vaccines cause autism also harms people with autism by diverting attention from efforts to support them in schools, clinics, and workplaces. Autism is a neurodevelopmental condition, not the result of vaccines or parental choices. As scientists and clinicians who work with children with autism and their families, we care deeply about accurate public health communication. Families trust institutions like the CDC to provide clear, evidence-based information. In this case, the CDC has failed to do so. The 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.