What is "thiomersal"

alt. A compound, chemical formula C₉H₉HgNaO₂S, used as an antiseptic and antifungal agent, especially in vaccines. n. A compound, chemical formula C₉H₉HgNaO₂S, used as an antiseptic and antifungal agent, especially in vaccines.

Thiomersal ( INN), commonly known in the U.S. as thimerosal, is an organomercury compound. This compound is a well established antiseptic and antifungal agent.

The pharmaceutical corporation Eli Lilly and Company gave thiomersal the trade name Merthiolate. It has been used as a preservative in vaccines, immunoglobulin preparations, skin test antigens, antivenins, ophthalmic and nasal products, and tattoo inks. Its use as a vaccine preservative was controversial, and it was phased out from routine childhood vaccines in the European Union, and a few other countries in response to popular fears. The current scientific consensus is that no convincing scientific evidence supports these fears.

In the U.S., Thiomersal has been removed from or reduced to trace amounts in all vaccines routinely recommended for children 6 years of age and younger with the exception of inactivated influenza vaccine. Vaccines with trace amounts of thiomersal contain 1 microgram or less of mercury per dose.