Thiomersal is an organic compound that is used as a preservative in some vaccines, pharmaceutical products, and topical antiseptics. It contains 49.6% mercury by weight and is used to prevent bacterial and fungal contamination of products. The World Health Organization recommends using thiomersal in certain vaccines because it is effective in low concentrations and is very stable. It is also used in some vaccines to reduce the number of doses needed, which helps to improve immunization rates. Thiomersal has been controversial due to concerns of possible side effects, but the scientific evidence does not support these concerns.
Thiomersal, also known as thimerosal (USAN, JAN) and merthiolate, is a substance with a history in both medicine and controversy [1]. Here's a breakdown:
What it is:
- Organomercury compound [1, 2].
- Well-established antiseptic and antifungal agent [1, 2].
Historical use in medicine:
- Preservative in some vaccines, particularly multi-dose vials [2, 3].
- Used to prevent bacterial and fungal contamination [2].
- Reduced or eliminated in many vaccines since the late 1990s due to safety concerns, though some still contain it [2, 3].
Safety Concerns:
- Revolves around the mercury content, though it's a different type (ethylmercury) than the one found in fish (methylmercury) [2, 4].
- Extensive research has found no link between thimerosal in vaccines and autism, the primary concern [2, 4].
Current Use:
- Limited use in some vaccines, primarily in developing countries [3].
- Still used as a preservative in some medications, cosmetics, and tattoo inks (although regulations vary) [1].