While pregnant woman are being told to get the H1N1 vaccine, some of the vaccine supply contains a preservative called Thimerosal, which is used in vials containing multiple doses. This preservative has mercury in it -- less than what's in a tuna fish sandwich, said one doctor. In Washington, the vaccines with Thimerosal can't be given to children ages 3 and younger, including those in the womb. Oregon does not have the same rule. To protect yourself and your children, officials say to ask for the single-dose vaccines. Note that if there is a shortage of these preservative-free vaccines, then everyone - including infants - would get the one with mercury.