Vaccines not linked to autism, second study reports

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An Institute of Medicine report has found no evidence that mercury-laced vaccines cause autism, as many parents of children with the disorder insist.

The institute, an affiliate of the National Academy of Sciences, is the second organization in six months to conclude there is no link between the brain disorder and a mercury-based vaccine preservative known as thimerosal. A probe by the Centers for Disease Control and Prevention (CDC), published in November, examined 124,000 babies and reached the same conclusion.

"Based on a thorough review of clinical and epidemiological studies, neither ... thimerosal nor the measles-mumps-rubella vaccine are associated with autism," said the institute's report, released yesterday.

Mercury is known to have toxic effects on the brain, and thimerosal was used for decades to stabilize vaccines.

The back-to-back findings of the institute and the CDC did not impress an advocacy group dedicated to removing mercury from medicine. Safe Minds, made up of parents of autistic children, said it was "disappointed" with the Institute of Medicine's results, which it deemed "premature" and based on "sloppy" research.

Rep. Dave Weldon, Florida Republican and a physician, shared those concerns. This report "may ultimately be repudiated ... it will do nothing to allay the concerns of thousands of parents of autistic children," he said.

Dr. Marie McCormick of Harvard University, who chaired the panel of scientists who studied the issue for the institute, said, "The overwhelming evidence from several well-designed studies indicate that childhood vaccines are not associated with autism.

"Further research to find the cause of autism should be directed toward other lines of inquiry that are supported by current knowledge and evidence and offer more promise for providing any answer," Dr. McCormick added.

Mark Blaxill, director of Safe Minds and the father of an 8-year-old autistic girl, said the institute's research was merely a "review of the current state of evidence" or literature on a possible link between mercury-based childhood vaccines and autism.

Mr. Weldon said the institute said in 2001 that it's "unclear whether ethylmercury (from vaccines) passes readily through the blood-brain barrier." He said the institute recommended some studies to "answer that question," but "these studies, in large part, were never done."

Mr. Blaxill said he hopes medical researchers ignore the institute's findings, which he fears "will suppress important scientific research" in an area that Safe Minds finds important.

Autism is characterized by sustained impairments in communication abilities and social interaction and by limited or repetitive patterns of behavior and interests.

The report said it's unclear how many cases of autism exist, but cited two reviews of published studies that say there is about one case for every 1,000 children.