Thimerosal in Vaccines: Why Is It in the News Again?
Thimerosal in vaccines is in the news again. Should you be concerned about getting vaccinated? Here are some answers to your questions about thimerosal and vaccines to help you make an informed decision.
What is thimerosal?
Thimerosal is used as a preservative in some drugs and biological products. For vaccines, preservatives are used to kill or prevent the growth of bacteria and fungi in containers that are used for more than one patient. This contamination has the potential to happen as a needle enters the rubber top of the vial multiple times to remove each dose.
Should I be concerned about thimerosal in vaccines?
Although thimerosal contains mercury, it is a different type (ethylmercury) than what is found in fish (methylmercury). Methylmercury can be toxic to people when exposed to large amounts. Ethylmercury leaves the body more quickly than methylmercury and is less likely to cause harm. The amount of mercury in a vaccine dose is about the same amount as in 3 ounces of tuna.
Thimerosal is not an active ingredient in vaccines.
Does thimerosal cause harm in humans?
Thimerosal has been used in vaccines since 1930. There has been no evidence of harm found in nearly 100 years of use.
In the past, concerns have been raised about a potential association between autism in children and the thimerosal content found in early childhood vaccines. After extensive research and expert review, no harm or association was found between use of thimerosal-preserved vaccines and autism in children. However, to address concerns it was recommended to remove thimerosal from all early childhood vaccines.
What is the current concern?
Today, there is a proposal to eliminate any remaining thimerosal-containing vaccines from the US market. This is not based on new safety concerns, but rather to expand the precaution from children to pregnant women, older adults, and those with high levels of mercury from workplace or other exposures.
Which vaccines contain thimerosal?
Very few vaccines contain thimerosal today as most have been changed to single use vials or prefilled syringes to reduce waste and allow for easy administration. These single use vaccines do not contain preservatives. No vaccines recommended for children have contained thimerosal since 2001.
The only remaining vaccines that contain small amounts of thimerosal are a few flu vaccine s that come in vials for use in multiple patients, but these account for only about 5% of all flu vaccines. A few others use thimerosal in the production of the vaccine, but only a trace amount remains in the final product.
What should I ask my pharmacist about thimerosal in vaccines?
If you are concerned about thimerosal in your vaccine, talk to your pharmacist. They can reassure you of a vaccine’s safety and tell you if it contains thimerosal as a preservative.
If you still are concerned, there may be vaccines available for you and your family that do not contain thimerosal. Do not skip getting a vaccine that will protect you against serious illness!