Summary
The federal government may soon advise against using flu vaccines that contain thimerosal, a mercury-based preservative. Despite most flu shots already being thimerosal-free, a CDC advisory panel suggests using vaccines without this ingredient. The preservative is mainly used in multi-dose vials, but it's been largely phased out due to safety concerns, even though there's no proven harm.
Key Facts
- Thimerosal is a preservative containing mercury and has been used in vaccines since the 1930s.
- The CDC’s advisory committee recommended using single-dose flu vaccines without thimerosal for children, pregnant women, and adults.
- Most flu vaccines today do not use thimerosal; 94% of the 2024-25 flu shots were thimerosal-free or reduced.
- The mercury in thimerosal is called ethylmercury, which breaks down more quickly than methylmercury, the harmful form found in seafood.
- Thimerosal helps prevent contamination in multi-dose vials, which are less common now.
- Thimerosal's use became less frequent after the 1997 FDA Modernization Act prompted a review of mercury in vaccines.
- The committee's decision follows a recent change where Health Secretary Robert F. Kennedy Jr. replaced all members of the advisory committee.
