Do vaccines contain mercury?
Almost all childhood vaccines DO NOT contain mercury. However, some influenza (flu) vaccines that have more than one dose in the vial (multi-dose vials) contain thimerosal, which is a mercury-based preservative. The small amount of thimerosal used to preserve vaccines is safe.
- Preservatives prevent germs (bacteria and fungus) from growing in the vial after the first dose has been removed.
- In the body, thimerosal is broken down into ethylmercury and thiosalicylate. Ethylmercury is different from methylmercury, the type of mercury found in the environment that can cause mercury poisoning.
- Ethylmercury is broken down and leaves the body much more quickly than methylmercury and is much less likely to build up in the body and cause harm. It has a half-life of seven days compared to 50 days for methylmercury. Half life means the amount of time it takes for half of the initial amount to break down.
- Studies have shown that thimerosal, at the levels found in vaccines, is easily eliminated from the body and does not cause neurological problems.
- In Canada, thimerosal is used only in some influenza vaccines provided in multi-dose vials. The amount of thimerosal is not greater than 50 µg per 0.5 mL dose. Thimerosal has not been included in any routine childhood vaccines produced since 2001. It was removed as a precautionary measure to maintain public confidence in vaccines, not because there was evidence that thimerosal in vaccines was dangerous.
- The evidence is clear that thimerosal in vaccines does not cause autism.
- A very small proportion of the population has a severe allergy (hypersensitivity) to thimerosal. For these people, thimerosal-containing vaccines should not be used; instead, single-dose formulations that are thimerosal-free are offered.
- The amount of mercury in a thimerosal-containing influenza vaccine is not more than 25 µg/dose. This is about the same amount as is found in a six-ounce can of Canadian albacore tuna, which has no serving limits and is considered safe to eat.
Date last reviewed:
Monday, Jan 31, 2022