Thimerosal is used as a preservative to prevent contamination of vaccine in multidose vials. Essentially, it kills any bacteria that may be introduced into a vial after multiple uses. This means that all brands are thimerosal free in single-dose form except Fluvirin made by Novartis, which contains an exceedingly small amount.
The question to ask your doctor is not which brand of flu shot they are using, but if the vaccine is a single use or if it was drawn from a multidose vial. If it’s a multidose vial, you should avoid it since all contain thimerosal to varying degrees. If it’s a single dose, it has no thimerosal. Below is a list of thimerosal-free vaccine brands. If you are pregnant, you should get the flu shot, not FluMist®.
Fluarix® Quadravalent, single dose
FluLaval® Quadravalent, single dose
Fluzone® Quadravalent, single (any dose, syringe/vial)
Afluria® , single dose
Fluarix® , single dose
FluLaval® , single dose
Fluzone®, single dose
Fluzone® Intradermal, single dose
Flucelvax®, single dose
Fluzone® High-Dose, single dose
FluBlok®, single dose
FluMist® Quadravalent Intranasal Spray, single dose