BRIEF REPORT Association Between Thimerosal-Containing Vaccine and Autism

HIGH DOSES OF MERCURIC COMpounds are nephrotoxic and neurotoxic. Thimerosal, an organic compound that contains ethylmercury, has been widely used since the 1930s as a preservative in certain vaccines. In the 1990s, an increasing number of different vaccines containing thimerosal were introduced in immunization schedules around the world, and thus the average cumulative exposure to thimerosal in infants has increased in recent years. This has led to the suggestion that childhood vaccination with thimerosal-containing vaccines increases the risk of neurodevelopmental disorders, such as autism, attention-deficit/hyperactivity disorder, and language and speech delay. In a recent independent review conducted by the Immunization Safety Committee, on behalf of the Institute of Medicine, it was concluded that the evidence was inadequate to accept or reject a causal relationship between thimerosal-containing vaccine and neurodevelopmental disorders. However, based on comparison with the toxicology of methylmercury, the biological plausibility of a link remained. Further research was recommended. We examined the hypothesized association by comparing children vaccinated with a thimerosal-containing pertussis vaccine with children vaccinated with the same pertussis vaccine formulated without thimerosal and following them with respect to development of autism and other autistic-spectrum disorders.