Thimerosal is a mercury-containing preservative that is used to prevent the growth of bacteria and fungi in vaccine vials. It is used for vials that contain many doses of vaccine. Thimerosal can also be used in the vaccine manufacturing process which can leave trace amounts of thimerosal in the final product.
Vaccines that contain thimerosal include Influenza and Hepatitis B but in very small amounts.
There are two types of mercury; methylmercury and ethylmercury.
Methylmercury is found in the environment through weathering of rocks, burning of coal, and volcanic eruptions. It makes its way through the food chain in fish, animals, and humans. In high levels it can be toxic to people.
Ethylmercury is the kind found in thimerosal. Studies suggest that it is broken down and passes through the body very quickly before it can do any harm – unlike methylmercury. Studies have also shown it does not accumulate in the body, again suggesting minimal harm.
The National Advisory Committee on Immunization (NACI) has reviewed the current scientific proof on the use of vaccines containing thimerosal and concluded that there is no legitimate safety reason to avoid the use of thimerosal-containing vaccines. Scientific evidence has not shown a relationship between thimerosal in vaccines and autism or other neurodevelopmental diseases.
Further resources can be found at the following site:
http://www.immunize.cpha.ca/en/publications-resources/contents.aspx
