A new study confirms there is no connection between the MMR vaccine and autism, reinforcing decades of consistent research on the topic. Researchers from the University of Washington (UW Medicine) analyzed 2.5 million pediatric medical records from 2015 to 2024. Their findings, published on October 4, 2026, in The Pediatric Infectious Disease Journal, show that receiving the MMR vaccine before age two does not increase the risk of autism spectrum disorder. This comes at a time when measles is making a comeback in the United States. The study used Cosmos, an electronic health record system that includes data from several American hospital networks. The research focused on minors whose birth records were linked to those of their parents. Children who were already diagnosed with autism before receiving the MMR vaccine were excluded from the study. The researchers used a method called "landmark age-anchored" analysis, which aligns all participants at the same developmental stage rather than using a fixed date. This approach helps eliminate a common issue in epidemiological studies known as the follow-up gap. In this sample, 91.4% of minors received the MMR vaccine before 24 months. The main result of the study showed an adjusted risk ratio of 0.97 (99% CI, 0.91 to 1.03), indicating that the risk of autism is statistically the same for vaccinated and unvaccinated individuals. However, the researchers noted several limitations, such as the fact that the study was observational. They also pointed out that family medical history was not available in the database and that children without a parent listed in the records were excluded. The idea that the MMR vaccine might be linked to autism dates back to 1998, when a British study involving twelve children suggested a connection between the vaccine, intestinal issues, and autism. This study was retracted in 2010 after it was discovered that the author had committed fraud and had financial conflicts of interest. The author was also stripped of his medical license in the United Kingdom. Since then, more than twenty cohort studies across multiple continents have found no association between the MMR vaccine and autism. Cognitive biases may explain why the myth has persisted. The early signs of autism often appear between 18 and 24 months, which is the same time when the MMR vaccine is typically administered. This temporal coincidence can create a false impression of a causal link, which only large-scale studies can dispel. The current prevalence of autism in the United States is about 3.2%, a figure that reflects the expansion of diagnostic criteria in the Diagnostic and Statistical Manual of Mental Disorders (DSM). In 2025, the United States recorded 2,289 cases of measles, the highest number since 1991. By mid-July 2026, the country had already reached that number again. Of those infected, 93% had not received any MMR vaccine or had an unknown vaccination status. American health officials believe the country has lost its measles eradication status, which was achieved in 2000. To prevent outbreaks, the threshold for herd immunity against measles is around 95%. When vaccination rates fall below this level, the virus can spread more easily. Several American counties have failed to meet this threshold since 2023.