Department of Health and Human Services: Public Health Service

JeroldF. Lucey , M.D .
Editorin Chief
PEDIATRICS
UniversityofVermont
Coll atiosdidia l Ofi ce
89 BeaumontAvenue , GIVEND201
Burlington , Vermont 05405- 0068

 

DearDr .

I am writing in support of an expedited review and consideration of the enclosed manuscript that examines the association between thimerosal, an ethyl mercury containing preservative, and autism. As you may know, there has been considerable interest by parents, clinicians, educators, and policy makers for an explanation of the marked increase in the rate of autism in recent years. A University of Davis study released in October of children identified through the California developmental disabilities service system, reemphasized the upward trend in autism and the lack of understanding as to the cause.

One factor hypothesized to have a causal role is childhood vaccinations. Specific aspects of vaccinations that have been subject to inquiry include the MMR vaccine and thimerosal. There are now numerous epidemiologic studies to suggest that the MMR. vaccine is not associated with the risk of autism; an Institute of Medicine review that was published in 2000 concluded that the weight of the scientific evidence did not support a link between MMR vaccine and autism.

For thimerosal, however, there are limited data to evaluate this factor. Because mercury in its inorganic form is known to have serious neurologic effects, many parents have speculated that the increased number of vaccines (many of which contained thimerosal) may have been a significant factor in the recent rise in autism. The Danish study is a powerful epidmeiologic study of this issue and capitalizes on the Danish health registry system that incorporates all health encounters into disease and exposure specific registries. In addition, a key strength of the study is the ability to examine rates of autism prior to and after the discontinuation of vaccines con-twining thimerosal in Denmark in 1992. Contrary to what would be expected if thimerosal was linked to autism, the authors did not observe a decline in the rate of autism with the removal of thimerosal containing vaccines.

I feel this is a very important study that deserves thoughtful consideration by the Journal. Its findings provide one strong piece of evidence that thimerosal is not causally linked to autism.
Thank you for your timely consideration.

Sincerely,

Jose F. Cordero, M.D., M.P.H.
Assistant Surgeon General
Director
National Center on Birth. Defects
and Developmental Disabilities