I believe I heard the amount of mercury is equal to the amount in a fish........the other ingredient ends in sol I believe, didn’t catch the whole name
American Constitutionalist got it pretty close, "thimerosol." It's a preservative. A significant number of people think the mercury in it (trace, if any) can cause serious metal trouble (autism, IIRC) if administered to children. Same folks have a strong aversion to amalgam dental filling material, for similar reasons. Google "thimerosol" and you'll find an abundance of debate, etc. on the subject.
I'm not going to take a flu vaccine, but my decision has nothing to do with thimerosol.
And they make it criminal to eat sugar now, but, they want to inject these HAZMATS in our bodies....