The Centers for Disease Control and Prevention (CDC) is weighing a potential recommendation to ban thimerosal, an ingredient found in some flu vaccines, due to concerns over its safety. However, experts argue that the risks associated with thimerosal are minimal and that there is no scientific evidence to support its removal from flu shots.
Here are four key things to know about thimerosal:
1. Thimerosal contains 50% mercury by weight and has been used as a preservative in vaccines since the 1930s. Its primary function is to prevent contamination between doses, which can be a risk for people with weakened immune systems.
2. Thimerosal has not been commonly used in flu vaccines since 2001, despite being removed from most childhood vaccines due to concerns over mercury exposure.
3. A link between thimerosal and autism has been repeatedly disproven by scientific studies. In fact, the removal of thimerosal from childhood vaccines did not result in a decrease in autism rates.
4. Most people will likely notice little difference if thimerosal is no longer recommended in flu shots, as most vaccines are now administered with single-dose syringes. However, manufacturers may need to adjust their supply chains and production processes.
The decision by the CDC to consider banning thimerosal from flu vaccines has sparked concerns among some health experts, who worry that it could undermine confidence in vaccines and make them less accessible.
Source: https://www.npr.org/sections/shots-health-news/2025/07/06/nx-s1-5454890/vaccine-ingredient-thimerosal-cdc-acip