Does thimerosal (mercury) in vaccines cause autism?
Here is what the checked sources say. Each title links to the original.
Vaccines are not associated with autism: an evidence-based meta-analysis of case-control and cohort studies
This meta-analysis combined five cohort studies of 1,256,407 children and five case-control studies of 9,920 children. No association was detected between thimerosal and autism (odds ratio 1.00, 95% CI 0.77 to 1.31), or between mercury from vaccines and autism (odds ratio 1.00, 95% CI 0.93 to 1.07). Vaccination overall and the MMR vaccine were also not associated with autism. The authors conclude that vaccines, and the thimerosal, mercury and MMR exposures studied, are not associated with autism or autism spectrum disorder.
Prenatal and infant exposure to thimerosal from vaccines and immunoglobulins and risk of autism
A case-control study in three US health plans, with autism diagnoses confirmed by in-person evaluations. Researchers measured each child's ethylmercury exposure from thimerosal-containing vaccines and immunoglobulins, before birth and through 20 months of age. Higher exposure did not raise the risk of autism spectrum disorder, autistic disorder, or autism with regression at any age window studied. The conclusion: early-life thimerosal exposure was not related to increased autism risk.
Vaccine Ingredients: Thimerosal
Explains that thimerosal contains ethylmercury, which the body clears faster than the methylmercury found in fish. It was removed from routine US childhood vaccines in the late 1990s, and in 2025 HHS required its removal from flu vaccines, the last US use. CHOP points to studies in which autism diagnoses kept rising after removal, as one piece of evidence alongside studies, including a 2004 Institute of Medicine review, that found no link to autism. Reviewed July 2026.