What You Need to Know About the CDC’s Move to Remove Thimerosal from Flu Vaccines

1. What is thimerosal?
   Thimerosal is a mercury-based preservative that’s been used since the 1930s to prevent contamination in multi-dose vaccine vials. It contains ethylmercury, which breaks down quickly in the body and is not the same as the more toxic methylmercury found in fish YouTube+14Medical News Today+14Al Jazeera+14.

2. Why it’s now being reconsidered:
   In June 2025, a newly formed CDC advisory committee recommended phasing out thimerosal from flu shots. They labeled it a “known neurotoxin” and advocated for single-dose, preservative-free formats to eliminate even theoretical risks Medical News TodayVerywell Health.

3. Health experts weigh in:

   • Most flu vaccines in the U.S. (about 96%) already do not contain thimerosal Al JazeeraAP News+1Verywell Health+1.

   • While the CDC, FDA, WHO, and other institutions have deemed thimerosal safe in the tiny amounts used Medical News Today+13Wikipédia+13Verywell Health+13, critics worry the shift could raise costs, reduce supply, and fuel vaccine hesitancy, especially in low-resource areas YouTube+7Medical News Today+7The Washington Post+7.

💡 Bottom line

Thimerosal has a long safety record, but its removal is driven more by caution and public perception than by evidence of harm. Still, it’s important to watch how this policy change could affect flu vaccine availability and public trust.