WASHINGTON - In a big blow to parents who believe vaccines caused their children's autism, a special U.S. court ruled Thursday that the shots are not to blame.
The court 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 ruled on Thursday.
The ruling was anxiously awaited by health authorities and families who began presenting evidence in June 2007.
More than 5,500 claims have been filed by families seeking compensation through the U.S. government's Vaccine Injury Compensation Program. The claims are reviewed by special masters serving on the U.S. Court of Claims.
"Hopefully, the determination by the special masters will help reassure parents that vaccines do not cause autism," the Department of Health and Human Services said in a statement.
A lawyer for the families did not respond immediately to a request for comment. But the head of one consumer group that questions vaccine safety, the National Vaccine Information Center, said the court's ruling will do little to change the minds of most parents who suspect a link between vaccines and autism. She said more studies are needed.
"I think it is a mistake to conclude that, because these few test cases were denied compensation, it's been decided vaccines don't play any role in regressive autism," said Barbara Loe Fisher, the centre's president.
To win, the families' lawyers had to show that it was more likely than not that the autistic symptoms in the children were directly related to a combination of the measles-mumps-rubella shots and other shots that at the time carried a mercury-containing preservative called thimerosal. The ruling means that families filing claims based on that theory -- potentially thousands -- aren't entitled to federal compensation, though they can appeal.
"It's a great day for science, it's a great day for America's children when the court rules in favour of science." said Dr. Paul Offit of the Children's Hospital of Philadelphia.
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 thimerosal, 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," one of the court's special masters wrote.
In 2001, parents of children with autism began filing petitions for compensation through the vaccine compensation program. Of the 12,850 cases ever filed through the program, about 5,535 represented autism cases.
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.
Under the government's vaccine compensation program, awards to the estate in a vaccine-related death are limited to US$250,000 plus legal fees and costs. Awards to individuals with an injury judged to be vaccine-related have averaged more than $1 million.
More than half a million U.S. children have autism with costly health care needs that often put a heavy financial strain on their families, national data show. Autism is characterized by impaired social interaction. Those affected often have trouble communicating, and they exhibit unusual or severely limited activities and interests.
