1. Home>
2. Specialties>
3. Pediatrics and Adolescent Medicine>
4. Summary and Comment

Thimerosal in Vaccines: Some Reassuring Data

The prevalence of autism in children did not decrease after thimerosal was removed from most vaccines.

Controversy persists about whether exposure to the preservative thimerosal (which contains ethylmercury) in childhood vaccines is responsible for the increased prevalence of autism, even after a 2004 review of 12 studies by the Institute of Medicine concluded that the evidence is weak for a link between thimerosal-containing vaccines and autism. The increasing concern about ethylmercury led to the removal of thimerosal from most vaccines in 1999 to 2001 (with the exception of some influenza vaccines). To examine whether removal of thimerosal led to a decrease in reported autism, researchers evaluated the number of new cases of autism by age reported to the registry of the California Department of Developmental Services from January 1995 through March 2007.

The prevalence of autism among children aged 3 to 12 years increased throughout the study period. Among children aged 3 to 5 years (the age at which the diagnosis of autism usually is established), the prevalence of autism increased each quarter during the study period.

Comment: These data from California, where a system for recording new cases of autism exists, indicate that the prevalence of autism in children did not decrease after the removal of thimerosal from most vaccines, suggesting that thimerosal-containing vaccines are not the primary cause of autism. The practice of withholding vaccines because of parents’ unsubstantiated beliefs about risks has increased in many communities. This report provides pediatricians with objective data to discuss with parents who are concerned about thimerosal-containing vaccines.

— Martin T. Stein, MD

Published in Journal Watch Pediatrics and Adolescent Medicine January 23, 2008

Citation(s):

Schechter R and Grether JK. Continuing increases in autism reported to California’s developmental services system: Mercury in retrograde. Arch Gen Psychiatry 2008 Jan; 65:19.

• Original article (Subscription may be required)
• Medline abstract (Free)