The U.S. Centers for Disease Control and Prevention (CDC) has recently updated its website regarding the relationship between vaccines and autism, a change initiated by Health and Human Services Secretary Robert F. Kennedy Jr. This revision suggests that the previous assertion that "vaccines do not cause autism" is "not an evidence-based claim," a statement that has sparked significant debate among public health experts.

On November 19, the CDC's updated webpage indicated a potential connection between vaccinations and autism, despite extensive research consistently finding no evidence to support such a link. The revised language states that scientific studies have not definitively ruled out the possibility that infant vaccines could contribute to autism, a claim that has been criticized for misrepresenting the scientific consensus.

Kennedy, in interviews, has expressed skepticism towards the established view that vaccines are thoroughly tested and safe, particularly regarding vaccines administered in the first year of life. He acknowledged that while numerous epidemiological studies have found no correlation between the measles, mumps, and rubella vaccine and autism, he believes there are deficiencies in the research surrounding vaccine safety. He emphasized that he is not claiming vaccines cause autism but rather that the evidence is insufficient to definitively prove they do not.

The CDC's revised statement retains a subheading asserting that "Vaccines do not cause Autism," but now includes an asterisk referencing an agreement with Republican Senator Bill Cassidy of Louisiana, who is a physician and vaccine advocate. Cassidy's support for Kennedy's nomination was contingent upon the retention of statements affirming vaccine safety.

Critics of the CDC's revision, including former agency leaders and current officials, have raised concerns about the implications for public health messaging and vaccine confidence, especially in light of recent outbreaks of vaccine-preventable diseases. Experts argue that the CDC's claims misrepresent the scientific process, as science cannot prove a lack of association. Dr. Paul Offit, a pediatrician and vaccine expert, reiterated that the overwhelming evidence supports vaccine safety.

The National Institutes of Health maintains that autism has no single cause, with multiple contributing factors, including genetics. The CDC's update has been described by some as a politicization of public health messaging, with calls for a return to evidence-based communication to protect community health outcomes.