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Pediatricians Argue to Keep Thimerosal in Some Vaccines


The U.N. Environment Program (UNEP) is discussing ways to lower environmental exposure to mercury, a chemical linked to developmental problems. Environmental groups supported by scientists argue that there is widespread global mercury contamination of seafood and consumers are experiencing health effects from methylmercury below the level that was considered "safe" a few years ago (see the EVISA News from December 9).

Photo: Daniel Paquet
Part of the proposal involves removing thimerosal, a mercury- based compound used as a preservative to maintain vaccine quality, from immunizations given to children around the world. Since the 1930s, at that time without any meaningful safety testing,  thimerosal has been used to prevent bacterial contamination of multidose vaccines. Since alkylmercurials are known to be strong neurotoxins, concerns have been raised in recent decades 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 inorganic methyl mercury. Since then, there is an ongoing controversy about the toxicity of methylmercury (found in fish) and ethylmercury (the component of thimerosal).

The discussion will continue during the fifth and final round of UNEP negotiations to put in place a legally binding global treaty to reduce mercury use and pollution. Despite ongoing controversy over the proposed policy, the legal text negotiated by the Intergovernmental Negotiating Committee is expected to be completed on 18 January 2013 in Geneva, Switzerland. 

The position of the American Academy of Pediatrics (AAP):
According to a statement published online December 17 in Pediatrics, 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 mercury treaty from the UNEP.

In her brief statement, 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.

Francis Walter A. Orenstein, the lead author of the AAP statement argues, that "we know a lot more about ethylmercury versus methylmercury. Ethylmercury, which is the form that is part of thimerosal, is excreted much more quickly and does not accumulate in the body in the same way than methylmercury does. When I talk to lay audience I often try to use the example of ethyl-alcohol and methyl-alcohol. There will be severe toxicity drinking a glass of anti-freeze, which contains methanol, whereas drinking a glass of wine that contains ethanol, is a lot safer. And so we learned  that thimerosal is safe..."

The writers of the AAP position statement further explained that while thimerosal is no longer used in many vaccines in the U.S., it "remains an important vaccine preservative in resource-poor countries," they wrote. "Thimerosal allows the use of multiuse vials, which reduce vaccine cost and the demand on already constrained cold-chain systems. Even in the United States, thimerosal could be critical for dealing with emergencies and the need to rapidly increase vaccine supply and delivery, such as during a serious pandemic of influenza.

The AAP position statement

Walter A. Orenstein, Jerome A. Paulson, Michael T. Brady, Louis Z. Cooper and Katherine Seib, Global Vaccination Recommendations and Thimerosal, Pediatrics; originally published online December 17, 2012; DOI: 10.1542/peds.2012-1760

Related information

Katherine King, Megan Paterson and Shane K. Green, Global Justice and the Proposed Ban on Thimerosal-Containing Vaccines, Pediatrics; originally published online December 17, 2012. DOI: 10.1542/peds.2012-2976

Louis Z. Cooper and Samuel L. Katz, Ban on Thimerosal in Draft Treaty on Mercury: Why the AAP's Position in 2012 Is So Important, Pediatrics; originally published online December 17, 2012. DOI: 10.1542/peds.2012-1823

 UNEP: Reducing Risk from Mercury
 FDA: Thimerosal in vaccines
 CDC: Thimerosal in Vaccines: A Joint Statement of the American Academy of Pediatrics and the Public Health Service
 Coalition for Mercury-free Drugs (CoMeD): Calls for Ban on Mercury in Vaccines
 Coalition for Mercury-free Drugs (CoMeD): Documents related to the use of thimerosal  in vccines
 Coalition for Mercury-free Drugs (CoMeD): The Viability of Using Non-mercury Preservatives in Vaccines
SafeMinds: Summary of Supportive Science Regarding Thimerosal Removal
 Vaccination News, March 14, 2011: Thimerosal Containing Vaccines, Part I

Related EVISA Resources

Link database: Toxicity of Organo-mercury compounds
Link database: Research projects related to organo-mercury compounds
 EVISA Link database: All about thimerosal (thiomersal)

Related EVISA News

October 12, 2012: Prenatal mercury intake linked to ADHD
October 28, 2011: WHO worries mercury treaty could affect costs and availability of vaccines
August 8, 2011: UNEP Global Mercury Treaty May Include Ban on Mercury in Medicine

June 19, 2011: Committee for Socio-economic Analysis agrees on two draft opinions on restriction proposals for mercury compounds under REACH
March 17, 2011: Researchers Urge the Removal of Mercury From Flu Shots

September 25, 2010: The European Chemical Agency (ECHA) calls for comments on reports proposing restrictions on mercury and phenylmercury
August 16, 2010: Methylmercury: What have we learned from Minamata Bay?
September 24, 2009: Huge field experiment for assessing human ethylmercury risk starting in october
July 15, 2009: New Study Finds: Thimerosal Induces Autism-like Neurotoxicity
May 15, 2008: New study will investigate the influence of environmental factors in autism
May 3, 2006: Texas Study Relates Autism to Environmental Mercury

last time modified: December 30, 2012


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