Thimerosal Information
Why is thimerosal used as a preservative in some vaccines?
Since the 1930s, it has been widely used as a preservative in a number of biological and drug products, including many vaccines, to help prevent potentially life threatening contamination with harmful microbes. Preservatives are not required for vaccines in single-dose vials. As a preservative, thimerosal is added at the end of the production process to the bulk or final container to prevent contamination after multi-dose vials are opened.Why are people worried about thimerosal?
Thimerosal contains a form of mercury called ethylmercury. In the 1990's, an increased number of thimerosal containing vaccines had been added to the infant immunization schedule. Concerns about the use of multiple thimerosal-containing vaccines in infants under 6 months of age had been raised.
All mercury isn't the same: methylmercury vs. ethylmercury
Mercury is a naturally occurring element found in the earth’s crust, air, soil and water. Since the earth’s formation, volcanic eruptions, weathering of rocks and burning of coal have caused mercury to be released into the environment. Once released, certain types of bacteria in the environment can change mercury to methylmercury. Methylmercury makes its way through the food chain in fish, animals, and humans. At high levels, it can be toxic to people.
Thimerosal contains a different form of mercury called ethylmercury. Studies comparing ethylmercury and methylmercury suggest that they are processed differently in the human body. Ethylmercury is broken down and excreted much more rapidly than methylmercury. Therefore, ethylmercury (the type of mercury in the influenza vaccine) is much less likely than methylmercury (the type of mercury in the environment) to accumulate in the body and cause harm.
In Summary...
In general, the doctors at Pediatric Associates all agree that we should minimize that amount of vaccines that contain thimerosal (All of our routine vaccines given are thimerosal free). But there are times, however, that the risk of not vaccinating far exceeds the hypothetical risk that thimerosal may pose.
For more information about thimerosal, click on the links below.
Thimerosal information from the FDA
Thimerosal Safety Information from Immunization Action Coalition