Is GAVI eliminating thimerosal vaccines due to dangers?

Recent news reports that GAVI, the charity that provides vaccines to people around the world, is eliminating vaccines with thimerosal (mercury) due to U.S. demands. So are thimerosal-containing vaccines dangerous?

Thimerosal is a mercury-based ingredient used in some vaccines to help stop bacteria and fungi from growing in multi-dose vaccine vials. Multi-dose vials are used for more than one shot, so they need extra protection from contamination.

In the United States, most vaccines come in single-dose vials. Because of this, most vaccines do not contain thimerosal. One exception can be some multi-dose flu vaccines. In lower-income areas, especially places where it is hard to keep vaccines cold, thimerosal may still be used to help keep vaccines safe.

Some people worry about thimerosal because it contains mercury. But not all types of mercury are the same. Thimerosal contains ethylmercury, which leaves the body quickly. This is different from methylmercury, the type of mercury found in some fish that can build up in the body over time.

Thimerosal has been used in vaccines, medicines, and contact lens solutions since the 1930s. Studies of babies, including premature and low-birth-weight babies, show that ethylmercury leaves the body quickly. About half of it is gone in three to seven days, and the rest leaves the body in stool. Within about a month after vaccination, mercury levels in the blood return to normal.

Research has also shown that thimerosal does not increase the risk of autism and does not harm the brain or body. Thimerosal was removed from most childhood vaccines in the United States in 2001, but autism diagnoses continued to rise after that. This is one reason scientists say thimerosal is not the cause of autism.

Gavi is working to remove thimerosal from vaccines, but NOT because thimerosal is dangerous. Instead, the decision is connected to funding concerns. Gavi’s goal is to keep vaccines available in countries that need them, especially where dangerous infectious diseases are still a major threat.