A retrospective cohort study following more than 2.5 million American children found no association between the timing of a child's first MMR vaccine dose before age 2 and a later autism diagnosis.
The study, published in the Pediatric Infectious Disease Journal, used the Cosmos electronic health record database covering children with linked birth-parent records from January 2015 through December 2024, with follow-up through age 8 or the last recorded visit. In the primary analysis of children who received a first dose between 11.5 and 24 months, the adjusted hazard ratio for autism was 0.97, with a 99% confidence interval of 0.91 to 1.03.
