Does the flu vaccine contain thimerosal?

Yes, the majority of influenza vaccines distributed in the United States currently contain thimerosal as a preservative. However, some contain only trace amounts of thimerosal and are considered by the Food and Drug Administration (FDA) to be preservative-free.

Manufacturers of preservative-free flu vaccine use thimerosal early in the manufacturing process. The thimerosal gets diluted as the vaccine goes through the steps in processing. By the end of the manufacturing process there is not enough thimerosal left in the vaccine to act as a preservative and the vaccine is labeled "preservative-free".

Last Reviewed: 10/18/2010

• What is thimerosal?
• Is thimerosal safe when used as a preservative in vaccines?
• How effective is the nasal-spray seasonal flu vaccine?
• Can a pregnant health care provider give the live nasal spray flu vaccine?

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    • Thimerosal