Over the last few years, tremendous attention has been placed on vaccine safety as more research finds connections between the mercury-based preservative used in childhood and adult vaccines and the development of neurologic and immunologic disorders. While commercially-available influenza vaccines contain thimersol, the importance seems to lie with the concentration.  Each season, the average adult will be offered multidose flu vaccine vials that contain 0.01% thimerosol as a preservative—or the mercury equivalent of 24.5 micrograms of mercury per dose. In contrast, the same size dose in an individual pre-filled syringe (a preservative-free flu vaccine with no added thimerosol) contains only 0.98 micrograms of mercury, about 25 times less than the multi-dose vial. We have a limited supply of these vaccines available to our patients, their families, and the general public.