There is no association between childhood vaccines that contain thimerosal and development of autism in children who received the vaccines, according to an article in the October 1st issue of the Journal of the American Medical Association.

According to background information in the article, thimerosal, a preservative used in some vaccine formulations, contains ethylmercury. It has been suggested that childhood vaccination with thimerosal-containing vaccine(s) could be causally related to neurodevelopmental disorders such as autism, attention deficit hyperactivity disorder, and speech and language delay.

In the current study, Anders Hviid, M.Sc., and his Danish colleagues studied children who were vaccinated with a thimerosal-containing pertussis vaccine and children vaccinated with the same pertussis vaccine formulated without thimerosal and compared these two groups with respect to development of autism and other autism spectrum disorders. The study included all children born in Denmark from January 1, 1990 to December 31, 1996 (a total of 467,450 children).

The researchers identified 440 cases of autism and 787 cases of other conditions on the autism spectrum. The risk of autism and other autism spectrum disorders did not differ significantly between children vaccinated with thimerosal-containing vaccine and children vaccinated with thimerosal-free vaccine. Furthermore, there was no indication of a dose-response association between autism and the amount of ethylmercury received through thimerosal.

The authors concluded that "The results do not support a causal relationship between childhood vaccination with thimerosal-containing vaccines and development of autistic-spectrum disorders."