IOM Reports That MMR and Thimerosal Do Not Cause Autism

The IOM Immunization Safety Review Committee released an updated report on Vaccines and Autism.  After careful review of data, made available in the past 3 years, the Committee has determined that "the body of epidemiologic evidence favors rejection of a causal relationship between thimerosal containing vaccines and autism.”  The Committee also concluded that “the body of epidemiologic evidence favors rejection of a causal relationship between MMR vaccine and autism." The IVS agrees with both conclusions.  These findings should come as no surprise to those who have carefully followed the hypothesis that MMR may cause autism.  There has been much confusion about thimerosal and autism. The IVS and others have raised appropriate concerns about the safety of bolus doses of thimerosal because methylmercury, a compound related to the ethylmercury found in thimerosal, is a known cause of learning disabilities in children born to women who have consumed large quantities of fish or other seafood contaminated with methylmercury.  There is also concern that exposure to multiple doses of ethylmercury could be additive to the effects of methylmercury. The EPA estimates that as many as 300,000 children are born every year in the United States to women with levels of methylmercury that are "of concern".  The potential effect of ethylmercury in thimerosal causing the same mild learning disabilities as methylmercury has been over-interpreted by some individuals as evidence that thimerosal causes autism; a much more complex and severe disorder.  The IOM safety committee was asked specifically not to review possible associations between thimerosal and mild learning disabilities.  There are ongoing epidemiologic studies (with results expected by the end of 2004) that should help shed light on whether or not there is evidence of thimerosal causing learning disabilities.  However, these studies may not address the key issue of possible additive effects between ethylmercury and methylmercury.  We strongly encourage studies in animals to address this key issue.

This page was last updated on August 02, 2010