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Autism Spectrum Disorders Health Center

Thimerosal Down but Autism Rising

Removal of Mercury From Child Vaccines Fails to Halt Autism Increase
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WebMD Health News
Reviewed by Louise Chang, MD

Jan. 7, 2008 -- Autism rates continue to go up despite removal of thimerosal, which contains a form of mercury, from nearly all child vaccines, California data show.

The finding adds to a growing body of evidence against the " thimerosal hypothesis." The hypothesis holds that vaccines using thimerosal as a preservative -- given to children or their mothers -- causes autism.

As a precautionary measure, by March 2001 thimerosal was removed (except for trace amounts) from all recommended infant vaccines. The only childhood vaccines that still contain more than trace amounts of thimerosal are multiple-dose vials of some flu vaccines.

An early look at data from California suggested that removal of thimerosal might have led to a decline in autism. But now an updated look at the data by the California Department of Public Health shows that there was no such decline.

"We are reassured that we found no link between routine childhood vaccination and increases in childhood autism in the data," California DPH Medical Officer Robert Schechter, MD, tells WebMD. "But the finding that there are increasing numbers of kids who need services is not reassuring. We support efforts to find preventable causes of autism."

The data are based on children referred to the California Department of Developmental Services System, a network of regional centers that serve people disabled by autism, mental retardation, and other developmental disabilities.

The most recent data come from March 2007, reflecting autism in children as young as age 3. Data on children younger than 3 are not routinely entered into the system. One 2001 look at the data by proponents of the thimerosal hypothesis suggested that there was a decline in autism beginning in 1994. A year earlier, a thimerosal-free Hib vaccine reduced the amount of thimerosal to which children were exposed.

But Schechter says there was no such decline.

"Not enough time had passed for autism in the younger children in that time period to be fully recognized," he says. "We saw with additional time, rather than going up and going down, autism rates continued to go up."

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