I believe that the flu vaccine is the only one that contains mercury in the form of Thimerosal (merthiolate). Most of us probably received way more mercury from Mercurochrome, which contains 26% mercury, applied to scrapes and scratches in our youth. Thimerosal is 49.6% mercury and there is at most 2 to 3 micrograms of thimerosal per milliliter of vaccine).