The original paper was fraudulent and retracted; large studies of millions of children show no link.
What the evidence shows
The claim traces to a 1998 Lancet paper by Andrew Wakefield linking the MMR vaccine to autism. It was later found to be based on manipulated data and undisclosed financial conflicts; the journal fully retracted it and Wakefield lost his medical licence.
The science since is overwhelming and one-directional. A Danish cohort study of over 500,000 children (Madsen et al., 2002) found no higher autism rate among the vaccinated, and a meta-analysis of more than 1.2 million children (Taylor et al., 2014) confirmed no association between vaccines — or their ingredients — and autism. This is about as settled as epidemiology gets: the vaccine–autism claim is refuted, and the belief has real costs in resurgent measles outbreaks.
Sources
Madsen, K. M., Hviid, A., Vestergaard, M., et al. (2002). A population-based study of measles, mumps, and rubella vaccination and autism.
New England Journal of Medicine, 347(19), 1477–1482
Among over 500,000 Danish children, MMR-vaccinated children had no higher risk of autism than unvaccinated children.
DOI: 10.1056/NEJMoa021134 →Taylor, L. E., Swerdfeger, A. L., & Eslick, G. D. (2014). Vaccines are not associated with autism: An evidence-based meta-analysis of case-control and cohort studies.
Vaccine, 32(29), 3623–3629
A meta-analysis of over 1.2 million children found no association between vaccination and autism.
DOI: 10.1016/j.vaccine.2014.04.085 →