Sept 20, 2004: Did the 2004 Institute of Medicine (IOM) report regarding the possible association between thimerosal-exposure and autism produce any new findings?

Until 1999, Thimerosal (ethylmercury) was present in over 30 vaccines. The 2001 IOM study on Thimerosal and neurodevelopmental disorders stated that the evidence is inadequate to accept or reject a causal relationship.  Case reports were uninformative with respect to causality, there were no published epidemiological studies, and unpublished studies provided weak and inconclusive evidence.  The public health response was to discard thimerosal vaccines on the shelf and remove thimerosal from other vaccines.  Thimerosal was removed from all recommended vaccines by March 2001. The National Vaccine Injury Compensation Program has 4100 claims pending alledge a causal linkage between thimerosal and autism.  

The 2004 IOM study reviewed all literature published since the 2001 report.  Of note was a Father/son team of attorneys, who were representing parents sueing for autism causation, published three papers.  They used the Vaccine Adverse Events Reporting System (VAERS) to calculate exposures and rates of autism.  Their papers lacked description of methods, the statistical results were not mathematically credible, and results were inconclusive with respect to causality. Publications reviewed included a controlled observational study from Denmark, a retrospective  cohort study based on 3 HMOs (Verstraten), 2 ecological studies, and the passive reporting of the VAERS have been published.  

The 2004 IOM conclusion was that “the evidence favors rejection of a causal relationship between thimerosal containing vaccines and autism.” Other recommendations included: --No change in licensure or recommendations for administration
-Better surveillance (track autism as thimerosal exposure declines)
-Quantify other sources of mercury exposure
-Restrict chelation to IRB-approved studies.

The response was impressive.  SafeMinds was outraged that the IOM report failed the American public.  They stated that the report violated nearly every tenet of medical science and that the committee chose to ignore groundbreaking scientific research on the mercury-autism link.  Many of the IOM committee members came under personal attacks and received threats.  Their last meeting was in an undisclosed place under heavy security.

(Just a reminder.  There is very little data on ethylmercury, which is the component in  thimerosal.  Toxicity issues have been based on the assumption that ethylmercury has the same toxicity as methylmercury.  There is absolutely no data that supports this assumption.)

All reports are available on the Immunization Safety Review Project’s Website:

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Donna Seger, M.D
Medical Director
Tennessee Poison Center