Association between thimerosal-containing vaccine and autism.
BACKGROUND
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.


METHODS
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.


METHODS
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).


CONCLUSIONS
The results do not support a causal relationship between childhood vaccination with thimerosal-containing vaccines and development of autistic-spectrum disorders.
D001321:Autistic Disorder / Q000139:chemically induced / Q000453:epidemiology*; D002648:Child; D002675:Child, Preschool; D015331:Cohort Studies; D003718:Denmark / Q000453:epidemiology; D004305:Dose-Response Relationship, Drug; D005035:Ethylmercury Compounds / Q000009:adverse effects; D006801:Humans; D007223:Infant; D016017:Odds Ratio; D011310:Preservatives, Pharmaceutical / Q000009:adverse effects*; D012042:Registries; D013849:Thimerosal / Q000009:adverse effects*; D014612:Vaccines / Q000009:adverse effects*
D005035:Ethylmercury Compounds; D011310:Preservatives, Pharmaceutical; D014612:Vaccines; D013849:Thimerosal