If you roam around the Web enough, you're likely to encounter scores of Web sites and bulletin-board posts about the supposed link between vaccines and autism spectrum disorders. Unlike other dubious notions, this one actually stems from something that appeared in a well-respected source.
In 1998, the Lancet, an esteemed British medical journal, published an article in which a researcher claimed that another type of vaccine -- the combined childhood inoculation for measles, rubella and mumps -- was linked to gastrointestinal disease and loss of developmental skills such as language [source: Wakefield et al.]. The article caused a stir, and some parents were reluctant to have their children vaccinated as a result. But according to a 2010 New York Times article, subsequent investigation raised questions about the researcher's ethics and methods, and the Lancet retracted the article. Subsequent studies have failed to show any link between vaccines and autism, the Times reported [source: Harris].
Some autism activists also have raised questions about thimerosal, a preservative containing mercury that has been used in some vaccines and other products since the 1930s. Since the seasonal flu vaccine is produced in large quantities for annual immunization campaigns, some multidose vials contain the preservative to protect against contamination once the containers are opened. According to the CDC, there's no scientific evidence that thimerosal causes any harm to people, except for minor reactions such as redness and swelling at the injection site. But regardless, there's no hazard to children, because only adults get the vaccine containing the preservative. The U.S. Food and Drug Administration eliminated the use of thimerosal in medications given to children back in 2001 [source: CDC].