The discussion is often heated, and emotional. Some have even claimed that the CDC is hiding information linking thimerosal use to conditions like autism, while others try to debunk the claim. The mercury-based preservative is indeed still in many vaccines, but is it safe?

Merck, GlaxoSmithKline, Sanofi Pasteur, and Novartis all still manufacture vaccines, which contain mercury, or thimerosal. It is even used in an influenza vaccine given to children as young as 6 years of age. Mercury is a known neurotoxin. The FDA calls thimerosal a 'mercury-containing organic compound . . . that has been widely used since the 1930s . . . as a preservative in many drugs, including vaccines."

They go on to say that due to concerns over neurotoxicity, thimerosal has been removed 'or reduced to trace amounts' in all vaccines routinely used on children 6 and younger, with the exception of the Influenza A vaccine (see Table 1).