Thiomersal
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Thiomersal, or thimerosal, is a mercury-containing compound used as a preservative in many vaccines. The fact that some mercury compounds are toxic has led many to conclude that vaccines containing this compound are dangerous.
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[edit] Mercury studies
Many mercury compounds -particularly those with mercury-carbon bonds- are neurotoxins, such as dimethylmercury.[1] While in large doses thiomersal can be toxic, a 2002 study indicated that the mercury levels in infants receiving a vaccine preserved by an appropriate amount of thiomersal were low; some were so low that they could not be measured. The blood concentrations were below the EPA guidelines. The amount of mercury in stool samples was high, indicating that the body eliminated the thiomersal and mercury concentrations in the blood fell back to levels prior to vaccination. This indicates that thiomersal has low bioaccumulative properties.[2][3]
Most of the concern about thiomersal derives from analogy from methylmercury, a well characterized mercury compound, but it is unclear whether the pharmacology is similar to thiomersal but still it was removed from use in 2002 as a precautionary measure. Initial studies on the pharmacokinetics indicate differences.[4]
[edit] Actual use of thiomersal
On January 1928, 42 children were injected with a diphtheria vaccine in Bundeberg, Austria. The first 21 were vaccinated from a fresh container of the TAM vaccine. Several days later, the same batch was used to inoculate a further 21 children; two days later 12 had died. This wasn't due to the dangers of the vaccine, but due to the fact that vaccines didn't contain preservatives of any kind. The lack of anti-bacterial agent in the sample of vaccine caused the second group of children to be injected with living staphylococci bacteria, which had grown inside the batch between injecting the first group and the second. From this point on, preservatives and anti-bacterial agents became an essential ingredient in vaccines and thiomersal is one of several effective preservatives. It seems ironic, then, for anti-vaccination groups who want "vaccine safety" to attack one of the compounds responsible for making vaccines extremely safe.[5]
The amount of thiomersal actually present in the vaccines is low. Most importantly, however, the large studies listed here that have shown no evidence of harm due to their use. Additionally, the only routine vaccine that still contains thiomersal is the influenza vaccine, therefore arguments against other routine vaccinations should not even invoke thiomersal.
[edit] See also
[edit] Footnotes
- ↑ http://www.fda.gov/cber/vaccine/thimerosal.htm
- ↑ Pichichero ME, Cernichiari E, Lopreiato J, and Treanor J. "Mercury concentrations and metabolism in infants receiving vaccines containing thimerosal: a descriptive study." Lancet 360:1737-1741 (2002).
- ↑ Web based summary of the above paper.
- ↑ Burbacher, TM; Shen, DD; Liberato, N; Grant, K.S.; Cernichiari, E; Clarkson, T. "Comparison of Blood and Brain Mercury Levels in Infant Monkeys Exposed to Methylmercury or Vaccines Containing Thimerosal" Environmental Health Perspectives 113: 1015-1021 (2005). http://www.ehponline.org/docs/2005/7712/abstract.html
- ↑ FDA.gov - Thimerosal in Vaccines
