Is there an association between thimerosal in vaccines and autism? Although the biomedical community and the courts in the United States have rejected this assertion, they have not convinced many vocal and well-intentioned parents that such a link does not exist. What is thimerosal (better known internationally as thiomersal), why has it been included in vaccines, and what is the current status of the controversy?
Thimerosal (Merthiolate) is an antibacterial and antifungal antiseptic, containing almost 50 percent mercury, which since 1927 has been applied to the skin. Since the 1930s, it has been added to multidose vials of some vaccines as a preservative to prevent their accidental microbial contamination. Mercury is a nerve poison. As a precautionary measure, in 1999, the Centers for Disease Control and Prevention (CDC) strongly encouraged vaccine manufacturers to reduce or eliminate thimerosal at the earliest possible date and, with few exceptions, this has been done in the United States, Canada, and Europe.
In its 2004 report, the National Academy of Science’s Institute of Medicine (IOM), incorporating data from Europe, concluded that no causal relationship exists between thimerosal-containing vaccines and autism. Medical groups in North America and Europe, the World Health Organization, and Autism Speaks support this position. Moreover, the medical community has expressed concern that while the dangers of thimerosal were speculative, there are far greater dangers of contracting such serious infectious diseases as measles, whooping cough, and bacterial meningitis if parents refuse the use of vaccines for their children or for influenza during pregnancy.
Parent groups, scientists, and personal-injury lawyers support a thimerosal-autism link by pointing to mercury health warnings, an increase in the number of vaccinations, and a dramatic ten-fold increase in the number of autism cases between 1996 and 2007.
In 1986, a “Vaccine Court” was established to protect vaccine makers from state-court lawsuits and provide funds to compensate parents of children who were injured by a vaccine. Whereas the U.S. Vaccine Court has failed to support claims by concerned parents, in 2010 a British medical panel backed the claim of a link between a vaccine and seizures in a child. The jury remains out.
SEE ALSO Smallpox Vaccine (1796), Polio Vaccine (1954), Gardasil (2006).
A number of parent groups have argued that thimerosal added to vaccines to prevent microbial contamination is responsible for autism in their children. This puzzle-patterned ribbon symbolizes autism awareness.