Not that I needed any further evidence to convince me that there is no link between the MMR vaccine and autism, but a new large US study provides more evidence that the link does not exist.

This study contradicts the recent changes to the CDC website, which obfuscates the lack of a link between vaccines and autism. Unfortunately, this messaging only confuses parents about vaccines, something we don’t need right now.

Given the growing numbers of measles cases in the USA, we need to have more convincing evidence that the MMR vaccine is safe and effective in protecting everyone from measles.

This brief post will examine the data from this new study, which will hopefully help some parents understand that the MMR vaccine is not linked to autism.

MMR vaccine and autism study

In a study published on 28 July 2026 in Pediatric Infectious Disease Journal, Todd L Burstain,
Dale Jacques, and Jennifer M Burstain, University of Washington Medicine, Seattle, used the Cosmos electronic health record database to examine the records of 2,560,035 children and linked parent information from January 2015 through December 2024. The scientists followed the children until age 8 or their last doctor’s appointment before the retrospective cohort study end date.

Here are the key results:

• In the primary 11.5- to 24-month cohort, the first MMR vaccination was not associated with an increased risk of autism.
• Across all age-specific cohorts, there was no association between the vaccine and increased risk of autism.
• The negative control analysis, a method used in research to identify and adjust for bias by employing a control that is not expected to be affected by the treatment or intervention being studied, showed a similar lack of association between the vaccine and autism.

The authors concluded

In this large US cohort, age-anchored landmark analyses show no association between MMR vaccination before 24 months and childhood autism. The concordant near-null findings for both MMR and a negative control exposure support that the observed results are unlikely to be explained by residual confounding. These findings highlight the importance of age-specific analytic approaches in evaluating vaccine safety using observational data.

Summary

Here’s another huge study, of over 2.5 million children, that shows that there is simply no link between the MMR vaccine and autism spectrum disorder.

I doubt that the anti-vaccine world will read this and change their mind, but let’s hope they do. This is a well-done study that uses impressively large sample sizes to show the MMR vaccine is safe.

I know what I am about to write annoys anti-vaxxers, but the lack of a link between the vaccine and autism is settled science. There is simply no good (or even bad) scientific evidence that shows a link.

On the other hand, we have hundreds of studies that clearly show that there is no link — this new study adds to that settled science.

Measles is a dangerous disease, despite the anti-vaccine claims that it isn’t. The MMR vaccine is the best protection against measles and also protects those who cannot get it.

A few years ago, someone replied to me on Twitter (it was Twitter then) that I shouldn’t waste my time talking about autism and vaccines because it was old news, and that the link had already been debunked. Here I am years later — still fighting the good fight, trying to convince everyone that the vaccine does not cause autism. I imagine I’ll be doing this for many more years.

Citations

• Burstain TL, Jacques D, Burstain JM. Association Between First MMR Vaccination Before Age 2 Years and Childhood Autism in a U.S. EHR Cohort of 2.5 Million Children. Pediatr Infect Dis J. 2026 Jul 28. doi: 10.1097/INF.0000000000005349. Epub ahead of print. PMID: 42520244.

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