Vaccine industry in panic over global effort to remove all mercury from vaccines
The controversy regarding the continued use of mercury in some vaccines, despite the element's proven toxicity, is coming to a head as the United Nations (UN) considers the passage of a new treaty that would outlaw the use of mercury in medicines worldwide. According...
Thimerosal, which is approximately 50% mercury by weight, has been one of the most widely used preservatives in vaccines. It is metabolized or degraded to ethylmercury and thiosalicylate. Ethylmercury is an organomercurial that should be distinguished from methylmercury, a related substance that has been the focus of considerable study (see "Guidelines on Exposure to Organomercurials" and "Thimerosal Toxicity", below).
At concentrations found in vaccines, thimerosal meets the requirements for a preservative as set forth by the United States Pharmacopeia; that is, it kills the specified challenge organisms and is able to prevent the growth of the challenge fungi (U.S. Pharmacopeia 2004). Thimerosal in concentrations of 0.001% (1 part in 100,000) to 0.01% (1 part in 10,000) has been shown to be effective in clearing a broad spectrum of pathogens. A vaccine containing 0.01% thimerosal as a preservative contains 50 micrograms of thimerosal per 0.5 mL dose or approximately 25 micrograms of mercury per 0.5 mL dose.
Prior to its introduction in the 1930's, data were available in several animal species and humans providing evidence for its safety and effectiveness as a preservative (Powell and Jamieson 1931). Since then, thimerosal has been the subject of several studies (see Bibliography) and has a long record of safe and effective use preventing bacterial and fungal contamination of vaccines, with no ill effects established other than minor local reactions at the site of injection.
While the use of mercury-containing preservatives has declined in recent years with the development of new products formulated with alternative or no preservatives, thimerosal has been used in some immune globulin preparations, anti-venins, skin test antigens, and ophthalmic and nasal products, in addition to certain vaccines. Under the FDA Modernization Act of 1997, the FDA compiled a list of regulated products containing mercury, including those with thimerosal (Federal Register 1999). It is important to note that this list was compiled in 1999; some products listed are no longer manufactured and many products have been reformulated without thimerosal. Updated lists of vaccines and their thimerosal content can be found in Table 1 (routinely recommended pediatric vaccines) and Table 3 (expanded list of vaccines).