A government-funded study on thimerosal is the latest in a series of research efforts to debunk the idea that childhood vaccinations caused autism.
"This study should reassure parents about following the recommended immunization schedule," the Centers for Disease Control's Dr. Frank Destefano, the study's lead author, told Reuters.
Debate over the safety of childhood vaccines surged more than a decade ago, when a small study by Dr. Andrew Wakefield warned that preventive shots -- in particular that for measles, mumps and rubella -- were linked to autism spectrum disorder.
Following Wakefield's study, which was published in prestigious medical journal The Lancet, parents worldwide stopped vaccinating their children. It was enough to spur several outbreaks of illnesses once believed eradicated in the Western world.
Rates of childhood measles in England and Wales, for example, soared by 80 percent between 2007 and 2008.
Wakefield's study was retracted by The Lancet earlier this year, after an independent review concluded that Wakefield had conducted his research "dishonestly and irresponsibly."
Still, neither that nor previous studies, including a 2004 report from the Institutes of Medicine, have significantly swayed frightened parents.
Researchers with the CDC tracked more than 1,000 children, born between 1994 and 1999. Of the study participants, 256 had been diagnosed with autism.
After reviewing immunization records of children and their mothers, the team compiled thimerosal exposure levels for each child, and concluded that there was absolutely no connection between vaccinations -- whether prenatally or after birth -- and the development of autism.
Questions persist, however, as to the precise cause of the condition, which is estimated to afflict 1 in 110 American children. In fact, rates of autism have increased since 2001, when most vaccine manufacturers eliminated thimerosal from their products.
This study actually found a small connection between increased thimerosal exposure and a reduced risk of autism, although the research team couldn't offer an explanation for the link.
Autism, which usually develops in the first few years of a child's life, can be devastating. Symptoms include social withdrawal, learning difficulties and unusual response to sensory information.
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Effective treatments for the condition continue to elude experts, although early intervention is now considered key in mitigating autism's potential severity.Whether advocates for the vaccine-autism link are convinced by the new report remains to be seen. In a comprehensive rundown of thimerosal's alleged dangers on its website, the National Autism Association appears emphatic in dismissing the CDC's credibility when it comes objective autism research.
"The CDC in general and the National Immunization Program in particular are conflicted in their duties to monitor the safety of vaccines, while also charged with the responsibility of purchasing vaccines for resale as well as promoting increased immunization rates," the website reads
