Question: Can vaccines cause autism?
The concern stems chiefly from the preservative thimerosal, a compound containing mercury. It was used in many vaccines until it was phased out in 2001 as part of an FDA-led campaign to reduce mercury exposure in children. Some people believe thimerosal is a neurotoxin, a substance that damages nerve tissue, and that it harms developing brains.
Cornelia Read of Exeter, New Hampshire, blames the ingredient for her daughter's autism. "Lila was perfectly fine -- talking, making eye contact and very social -- until she was 13 months old," says Read. "Now, at age 15, she is nonverbal and cognitively about the level of a 1-year-old." Read became suspicious of thimerosal after reading an article depicting autism as a form of mercury poisoning.
Though thimerosal has been ousted from most vaccines (it's still used in some versions of the flu shot), some parents continue to blame the rise in autism and other developmental disorders on environmental toxins they claim the shots contain.
Facts: "There are a large number of well-designed studies involving thousands of children over the past decade that show no connection between vaccines and neurodevelopmental problems such as autism and ADHD," says Jeanne Santoli, M.D., deputy director at the CDC's National Immunization Program. Even after thimerosal was removed from most vaccines, autism rates have continued to climb. "You'd expect that if a link was there, we'd have seen a decrease after thimerosal was removed," Santoli says. "But we've seen no such drop-off." It's important to note that methylmercury, which contaminates fish and pollutes lakes, can build up in the body and lead to nerve damage; but thimerosal contains ethylmercury, a different type of mercury that is much less likely than methylmercury to accumulate in the body and has not been shown to have adverse effects.
Earlier this year, the U.S. Court of Federal Claims ruled that vaccines do not cause autism, rejecting the high-profile cases of three unrelated plaintiffs. The rulings found no evidence that the MMR shot, which immunizes children against measles, mumps and rubella, had caused the children's disorders.