Loren, for the most part, the entire argument against vaccines, and particularly as it relates to Autism, hinges exactly on the topic of mercury used as a preservative in vaccines. The preservative that you mention is known as thimerosal. Quoting directly from the CDC's own page [http://www.cdc.gov/vaccinesafety/Concerns/thimerosal/]: "Since 2001, with the exception of some influenza (flu) vaccines, thimerosal is not used as a preservative in routinely recommended childhood vaccines." "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. 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." Most of this manufactured controversy stems from a single journal article in a 1997 study published by Andrew Wakefield, a British surgeon. The article was published in The Lancet, a prestigious medical journal, suggesting that the measles, mumps, rubella (MMR) vaccine was increasing autism in British children. The paper has since been completely discredited due to serious procedural errors, undisclosed financial conflicts of interest, and ethical violations. Andrew Wakefield lost his medical license and the paper was retracted from The Lancet. If you care to read any of the studies in the area to prove any of the claims for yourself, try: https://scholar.google.com/scholar?q=thimerosal+and+autism&hl=en&as_sdt=0&as_vis=1&oi=scholart&sa=X&ved=0CBsQgQMwAGoVChMIgd3Pjej0xgIVws6ACh3RTw2x If you're not motivated to plumb the depths of the journal articles, thic mic.com post does a pretty good job of summing up some of the other "controversies" and provides links to specific journal articles as well: http://mic.com/articles/85725/7-biggest-lies-spread-by-the-anti-vaccine-movement-debunked-by-science