What is Thimerosal?
Thimerosal, also known as ethylmercury, is a preservative used in some types of influenza vaccines that the human body can process with minimal risk. Ethylmercury is sometimes confused with methylmercury, a higher-risk mercury compound that is not used in vaccines.
Understanding Thimerosal Use
Vaccines are contained in a small glass bottle called a vial, which can either hold a single dose or multiple doses of a vaccine. A single-dose vial is used for a single injection in one person, while a multiple-dose vial contains multiple vaccine doses and can be used for more than one dose administration. Preservatives, like thimerosal, may be used in multiple-dose vials to prevent the growth of bacteria or fungi once the vial is opened.
Flu and Pediatric Vaccines
Thimerosal is used in a small percentage of multiple-dose flu vaccines. Most flu vaccines are administered from a single-dose vial – only 4% of flu doses are packaged in multiple-dose vials. While used infrequently in vaccines, extensive research demonstrates that thimerosal is a safe additive.
Thimerosal is not used in any vaccine on the AAP’s childhood vaccination schedule.
Thimerosal Safety
There is no scientific evidence that thimerosal is harmful or causes autism. In 1999, as a precaution, the American Academy of Pediatrics, the Public Health Service agencies, and vaccine manufacturers agreed to reduce or eliminate thimerosal from vaccines. As a result, thimerosal has not been used in any vaccine on the AAP’s childhood vaccination schedule since 2001.
