Does the MMR vaccine cause autism?
Here is what the checked sources say. Each title links to the original.
Measles, Mumps, Rubella Vaccination and Autism: A Nationwide Cohort Study
Danish researchers followed 657,461 children born 1999 to 2010 using national health registries; 6,517 were diagnosed with autism. Vaccinated children had no higher autism risk than unvaccinated children (adjusted hazard ratio 0.93, 95% CI 0.85 to 1.02). There was also no consistent increase in risk in subgroups, including children with a sibling who had autism, children with other autism risk factors, or any time window after vaccination. A stated limitation: individual medical charts were not reviewed.
Vaccines for measles, mumps, rubella, and varicella in children
This Cochrane review pooled 138 studies with over 23 million participants. It found no link between MMR and autism (rate ratio 0.93, 95% CI 0.85 to 1.01; 2 studies, about 1.19 million children; moderate certainty). It does confirm real but rare harms: febrile seizures in roughly 1 per 1,150 to 1,700 doses, and a blood-clotting condition (ITP) in about 1 per 40,000 doses, which is less often than after natural infection. One measles dose was 95% effective.
Vaccines and autism
A plain-language page explaining where the MMR-autism worry came from: a 1998 paper by Andrew Wakefield describing 12 children, later retracted for scientific misconduct. It then walks through the studies that tested the idea, including 537,303 Danish children (Madsen), over 650,000 Danish children (Hviid 2019), and about 100,000 younger siblings, including children whose older sibling had autism (Jain 2015). None found a higher autism risk in vaccinated children. Reviewed September 2025.