Association between thimerosal-containing vaccine and autism

JAMA. 2003 Oct 1;290(13):1763-6. doi: 10.1001/jama.290.13.1763.


Context: Mercuric compounds are nephrotoxic and neurotoxic at high doses. Thimerosal, a preservative used widely in vaccine formulations, contains ethylmercury. Thus it has been suggested that childhood vaccination with thimerosal-containing vaccine could be causally related to neurodevelopmental disorders such as autism.

Objective: To determine whether vaccination with a thimerosal-containing vaccine is associated with development of autism.

Design, setting, and participants: Population-based cohort study of all children born in Denmark from January 1, 1990, until December 31, 1996 (N = 467 450) comparing children vaccinated with a thimerosal-containing vaccine with children vaccinated with a thimerosal-free formulation of the same vaccine.

Main outcome measures: Rate ratio (RR) for autism and other autistic-spectrum disorders, including trend with dose of ethylmercury.

Results: During 2 986 654 person-years, we identified 440 autism cases and 787 cases of other autistic-spectrum disorders. The risk of autism and other autistic-spectrum disorders did not differ significantly between children vaccinated with thimerosal-containing vaccine and children vaccinated with thimerosal-free vaccine (RR, 0.85 [95% confidence interval [CI], 0.60-1.20] for autism; RR, 1.12 [95% CI, 0.88-1.43] for other autistic-spectrum disorders). Furthermore, we found no evidence of a dose-response association (increase in RR per 25 microg of ethylmercury, 0.98 [95% CI, 0.90-1.06] for autism and 1.03 [95% CI, 0.98-1.09] for other autistic-spectrum disorders).

Conclusion: The results do not support a causal relationship between childhood vaccination with thimerosal-containing vaccines and development of autistic-spectrum disorders.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Autistic Disorder / chemically induced
  • Autistic Disorder / epidemiology*
  • Child
  • Child, Preschool
  • Cohort Studies
  • Denmark / epidemiology
  • Dose-Response Relationship, Drug
  • Ethylmercury Compounds / adverse effects
  • Humans
  • Infant
  • Odds Ratio
  • Preservatives, Pharmaceutical / adverse effects*
  • Registries
  • Thimerosal / adverse effects*
  • Vaccines / adverse effects*


  • Ethylmercury Compounds
  • Preservatives, Pharmaceutical
  • Vaccines
  • Thimerosal