MONDAY, Sept. 13 (HealthDay News) -- Infants exposed to the highest levels of thimerosal, a mercury-laden preservative that used to be found in many vaccines, were no more likely to develop autism than infants exposed to only a little thimerosal, new research finds.
The study offers more reassurance to parents who worry that vaccination raises their children's risk for autism, the researchers said.
"Prenatal and early life exposure to ethylmercury from thimerosal in vaccines or immunoglobulin products does not increase a child's risk of developing autism," concluded senior study author Dr. Frank DeStefano, director of the immunization safety office at the U.S. Centers for Disease Control and Prevention.
The study was released online Sept. 13 in advance of publication in the October print issue of Pediatrics.
Thimerosal has been used as a preservative in vaccines since the 1930s, according to background information in the article.
Concerns about the chemical began to crop up in 1999, when the U.S. Food and Drug Administration said that because of the increased number of thimerosal-containing vaccines added to the infant vaccination schedule, infants may be exposed to too much mercury. Thimerosal used to be found in hepatitis B, Hib (Haemophilus influenzae type B) and DTP (diphtheria, tetanus, pertussis) vaccines, among others.
During the ensuing years, the FDA worked with manufacturers to eliminate thimerosal from vaccines, according to the agency's Web site. Today, thimerosal has been removed or reduced to trace amounts in all vaccines routinely recommended for children 6 years of age and younger, with the exception of inactivated seasonal flu vaccine, according to the FDA. Parents who are concerned about thimerosal can ask for a preservative-free version, DeStefano said.
And thimerosal wasn't the only proposed autism-vaccine link. A 1998 pape
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