<a href="http://www.cdc.gov/vaccinesafety/Concerns/thimerosal/index.html" rel="nofollow">http://www.cdc.gov/vaccinesafety/Concerns/thimerosal/index.h...</a><p>Thimerosal is a mercury-containing preservative used in some vaccines and other products since the 1930's. There is no convincing evidence of harm caused by the low doses of thimerosal in vaccines, except for minor reactions like redness and swelling at the injection site.<p>However, in July 1999, the Public Health Service agencies, the American Academy of Pediatrics, and vaccine manufacturers agreed that thimerosal should be reduced or eliminated in vaccines as a precautionary measure.