tiny doses of a mercury compound called thimerosal keep multidose vials of flu vaccine safe from contamination with bacteria. before thimerosal was added to multidose vials contamination caused serious adverse events. exhaustive studies fail to find any reason to believe that thimerosal is unsafe. but if you don't want thimerosal you don't have to have it. single-dose syringes of flu vaccine don't need thimerosal and don't have any. neither does the flumist nasal spray vaccine. if you prefer a thimerosal-free vaccine check with your provider to see if one is available. if not check with your state or local health department to see where you can find one.
i know studies show flu vaccines preserved with thimerosal are safe but is there an alternative?