Thiomersal

Thiomersal is an organic compound with the formula C9H14O2S. It is a colorless to pale yellow liquid that is miscible with water. Thiomersal is a mercury-containing compound that was used as a preservative in multidose vaccines, particularly in influenza vaccines, to prevent bacterial contamination. It works by inhibiting the growth of bacteria and other microorganisms.

The use of thiomersal in vaccines was discontinued due to concerns about potential adverse effects, particularly in children. These concerns were based on a small number of studies suggesting a possible link between thiomersal exposure and autism spectrum disorders. However, numerous large-scale studies and reviews by independent organizations, including the Institute of Medicine and the Centers for Disease Control and Prevention, have found no consistent evidence of a causal relationship between thiomersal and autism.

Thiomersal is rapidly metabolized in the body and is excreted primarily in the urine. The half-life of thiomersal in the body is approximately 20-30 days. The primary metabolite of thiomersal is ethylmercury, which is also rapidly excreted.

Thiomersal is classified as a potential human carcinogen by the International Agency for Research on Cancer. However, the risk of cancer from thiomersal exposure is considered to be low, and the benefits of thiomersal as a preservative in vaccines were outweighed by the potential risks of bacterial contamination.

As of 2001, thiomersal was removed from all influenza vaccines in the United States. Other vaccines that contained thiomersal, such as the hepatitis B vaccine, were reformulated to remove thiomersal. The removal of thiomersal from vaccines has been credited with reducing the incidence of bacterial contamination in vaccinated populations.