AAP supports use of thimerosal in vaccines

The American Academy of Pediatrics (AAP) has endorsed the recommendation of the World Health Organization (WHO) Strategic Advisory Group of Experts on Immunization to retain the use of thimerosal as a preservative in vaccines.

WHO says that the preservative should not be considered a hazardous source of environmental mercury and should not be banned in multidose vials of vaccines as proposed by the United Nations Environmental Programme. Thimerosal contains ethyl mercury but in small quantities that if disposed of responsibly as hospital waste would pose minimum danger to the environment.

Thimerosal has been used in vaccines for more than 60 years. WHO maintains that replacing thimerosal with another preservative may affect the quality, safety, and efficacy of vaccines in multiuse vials and would affect mass immunization programs in developing countries if these vials were not available.

With its endorsement, the AAP is reversing its earlier position released in 1999 that called for eliminating mercury in vaccines, a decision that was based on US Environmental Protection Agency guidelines for safe limits of elemental, inorganic, or methyl mercury. At that time, there were no specific data on the safety of ethyl mercury in the form of thimerosal, which led to public anxiety about the accumulative effects of thimerosal preservative in infant vaccines and polarity between vaccine advocates and parents who believed that their children had been harmed.

The concern that ethyl mercury in thimerosal would accumulate in the body at a toxic rate similar to methyl mercury, a known neurotoxin, proved unfounded. Since 1999, pharmacology and toxicology studies have documented the differences between ethyl and methyl mercury, and efforts to produce credible evidence that thimerosal in vaccines presents any risk to human health have failed.

The global environmental treaty that would restrict human and environmental exposure to mercury is set to be finalized in January 2013. Both the Pediatric Infectious Diseases Society and the International Pediatric Association have endorsed the WHO recommendation.