AN INVESTIGATION INTO THE SUPPOSED LINK BETWEEN
THIMEROSAL-CONTAINING VACCINES AND AUTISM
RUPALI AVASARE, CHRISTINA FUENTES, LYNN NGO
BE.104—May 10, 2005
Thimerosal, a mercury-containing preservative used in vaccines, was implicated in 1997 to be
linked to autism.
Recent in vitro studies suggest that the concentration of thimerosal, and
subsequently ethyl mercury, present in vaccines is not cytotoxic.
A paucity of studies done
specifically with thimerosal has led lawmakers to base regulations on the toxicological profile of
However, recent in vivo studies show a marked difference in the toxicological
profiles of ethyl mercury, a metabolite of thimerosal, and methyl mercury. Neither in vitro nor in
vivo studies, then, implicate thimerosal as a toxic agent at the concentrations present in vaccines.
Epidemiological studies have been conducted in various countries assessing if a causal
relationship exists between autism and thimerosal-containing vaccines. Though there is a
concern that the ethyl mercury in thimerosal may cause neurotoxicity, which may lead to autism,
large scale epidemiological studies have not been able to support this claim.
In 2004, after
critical review of major epidemiological studies, the Institute of Medicine’s Immunization Safety
Committee released a report stating that a relationship between autism and mercury was not
found. The media, however, (mainly small, local sources) have disproportionately covered
stories supporting a link, taking advantage of the desperation felt by those personally affected by
autism in order to increase sales.
This, in turn, has caused many parents, especially parents of
autistic children, to be hesitant to vaccinate their children.
In order to address this, thimerosal
was removed from all vaccines in the US market. While not justified in terms of reducing the
risk of autism, the removal of thimerosal was justified in that it ensures that mislead parents will
continue to vaccinate their children.