By KEVIN FREKING
Associated Press

WASHINGTON - A special vaccine court ruled against parents with autistic children Thursday, saying that vaccines are not to blame for their children's neurological disorder.

The judges in the cases said the evidence was overwhelmingly contrary to the parents' claims - and backed years of science that found no risk.

"It was abundantly clear that petitioners' theories of causation were speculative and unpersuasive," the court concluded in one of a trio of cases it ruled on Thursday.

The ruling, which was anxiously awaited by health authorities, was a blow to families involved in more than 5,000 claims for compensation through the government's Vaccine Injury Compensation Program. The claims are reviewed by special masters serving on the U.S. Court of Claims.

To win, the families' attorneys would have to have shown that it was more likely than not that the autism symptoms in the children were directly related to a combination of the measles-mumps-rubella shots and other shots that at the time of vaccination carried a mercury-containing preservative called thimerosal.

But the court concluded that "the weight of scientific research and authority" was "simply more persuasive on nearly every point in contention."

The court still has to rule on separate claims from other families who contend that rather than a specific vaccine combination, the lone culprit could be thimserosal, a preservative that is no longer in most routine children's vaccines. But in Thursday's rulings, the court may have sent a signal on those cases too.

"The petitioners have failed to demonstrate that thimerosal-containing vaccines can contribute to causing immune dysfunction," a judge wrote about one theory that the families proposed to explain how autism might be linked.

In 2001, parents began filing petitions for compensation through the vaccine compensation program. In all, more than 5,300 claims were eventually filed alleging that vaccines caused autism or autism-like symptoms.

The petitioners originally sought to present three different theories of how vaccines could cause autism. For each theory, there were to be three test cases.