The American Academy of Pediatrics has endorsed the World Health Organization's stance that thimerosal -- a mercury-based preservative -- should be left in vaccines and should not be subject to a ban contained in a draft treaty from the United Nations Environment Program (UNEP). In a brief statement published online in Pediatrics, the academy supported the recommendations drafted by the WHO's Strategic Advisory Group of Experts (SAGE) on immunization at an April meeting. An AAP spokesperson said that the endorsement was adopted unanimously by the academy's infectious diseases committee. The Pediatrics Infectious Diseases Society and the International Pediatric Association have also thrown their support behind the guidance.
In 2009, UNEP requested that an Intergovernmental Negotiating Committee develop a binding treaty to reduce the hazards of environmental mercury. Included in the draft treaty, which will be debated and possibly finalized next month, is a provision banning the use of thimerosal in vaccines. The WHO has called for the removal of that provision, with SAGE concluding that although it supports efforts to reduce environmental mercury, "it is essential that access to thimerosal-containing vaccines is not restricted under this global initiative."
An Evolving Position on Thimerosal
Thimerosal has been used to prevent the growth of bacteria and fungi in multidose vials of vaccines since the 1930s. In recent decades, concerns have been raised about the potential neurotoxic effects of the preservative and a possible association with autism because it contains mercury in the form of organic ethyl mercury. The FDA tackled the issue in the late 1990s, and its review showed that the cumulative amount of mercury from vaccines included in the routine immunization schedule for infants could exceed the safety threshold set by the U.S. Environmental Protection Agency based on studies of methyl mercury. The amount did not, however, rise above the thresholds established by federal guidelines from the Agency for Toxic Substance Disease Registry and the FDA.
Based on those findings, and in addition to growing public pressure driven by congressional hearings and increasing media attention on potential adverse neurodevelopmental effects of thimerosal, the AAP and the U.S. Public Health Service (USPHS) in 1999 called for the removal of mercury from all vaccines. "Once the FDA calculations revealed that even one federal guideline was exceeded, the AAP and USPHS were obligated to full public disclosure," explained Louis Cooper, MD, of Columbia University in New York City, and Samuel Katz, MD, of Duke University in Durham, N.C., in a commentary accompanying the academy's current endorsement.
"With that disclosure, it was important to demonstrate a response that could prevent exceeding the guideline levels and also to continue to protect infants by still ensuring full immunization," wrote Cooper, a member of the AAP board of directors in 1999, and Katz, a former chair of the academy's infectious diseases committee. "The joint statement met those obligations while demonstrating an abundance of caution: putting safety first." By 2001, thimerosal had been removed from most vaccines in the U.S. and other high-income countries; it can still be found in some seasonal influenza vaccines and other adult vaccines. In areas of the world with fewer resources, however, thimerosal is still widely used as a vaccine preservative.
Vaccine Exemption Forms