LCromwell,   Thanks for your question.  Unfortunatey, your source is correct that some of the flu vaccines available today contain mercury.  The mercury is contained in an antiseptic called Thimerosol, which has been used since the 1930s to prevent the growth of bacteria within vaccines.  As you are probably aware, there has been speculation in the last few years that there may be a link between Thimerosol and autism.  The FDA recently awarded a large settlement to a family, but refused to acknowledge whether this link existed.  As a result of this concern, many companies are now producing vaccines without thimerosol, and most childhood vaccines are free of this antiseptic.    There are a few companies that are producing flu vaccine that is also free of thimerosol.    When obtaining a flu shot, ask whether the formulation contains thimerosol?.  If they refuse to tell you, find another place to get the shot.  As an adult, the risk is very low for developing a problem from this additive.  But if you have concerns, be sure to ask the question.   Hope this has been helpful.   Martin Cane, M.D.