Study: Ethylmercury Preservative in Vaccines Does Not Affect Neuropsychological Functioning

A series of papers published in the most recent issue of New England Journal of Medicine (study 1, study 2, study 3) suggest that exposure to thimerosal, an ethylmercury-containing preservative in vaccines, does not reduce neuropsychological functioning in children who are given vaccines or Rh globulins.

William W. Thompson, Ph.D., of the CDC, and colleagues, reported that there is no link between kids exposed to thimerosal and neuropsychological damage.

The results came from a study of 1,047 children, seven to 10 years old, from four HMOs that participated on what is known as the CDC's Vaccine Safety Datalink, a program designed to enhance the security of vaccines and biological agents.

Forty-two (42) neuropsychological tests were assessed. Only a few significant associations of any kind were identified, none important. The overall pattern of this study suggested that any significant associations encountered may come from chance findings due to the large number of statistical tests performed.

The investigators also wrote "the study did not examine the possible association between autism and exposure to mercury from vaccines and immune globulins."

This comes as a surprise since thimerosal is a believed to be the cause of some cases of autisms. A legal battle is going on in courts in regard to this issue. In 2000 parents started several advocacy groups based on the belief that thimerosal had caused their children's autism.

In 1999, the CDC and the American Academy of Pediatrics asked pharmaceutical companies to remove thimerosal from vaccines as soon as possible and in the interim asked physicians to delay the birth dose of hepatitis B vaccine for children not at risk.

Stephen D. Sugarman, J.D., of the University of California at Berkeley, reviewed the legal battles now being waged over vaccines and autism and published his results in the NEJM.

He did not see an end to the litigation at this point and he believes that it is unlikely that that the battles over vaccines and autism will end.