Lawyers have chosen nearly 4,900 families — each of which claim that the mercury-containing preservative thimerosal in vaccines brought about autism and other developmental disorders in their children — in an effort to seek this compensation from the government.
Past studies in Denmark, and more recently California, have suggested that thimerosal was not to blame, as reported cases of autism have continued to increase after the removal of thimerosal from most vaccines.
Dr. Pauline Filipek, associate professor of clinical pediatrics and neurology at the University of California Irvine School of Medicine, and her colleagues are researchers who are among those looking into a possible connection.
"Mercury has long been known to be a mitochondrial toxin, and could potentially interact with underlying genetic vulnerability of deficient mitochondria," she said. "That said, there remains no epidemiological data that we are aware of that implicates vaccination in autism or in mitochondrial disorders."
Boyd Haley, a chemist at the University of Kentucky and vocal proponent of a vaccine-autism link, believes the current studies are flawed. And he said that he believes this case, as well as most other cases of autism, are indeed the result of an underlying genetic vulnerability being triggered by the mercury that used to be present in vaccines.
"I am very pro-vaccine," Haley said. "I strongly believe in vaccination. I just believe that they ought to be safe and they ought to be tested."
Specifically, Haley said certain genetic conditions may make some children unable to effectively manufacture glutathione, a protein he says would allow them to clear substances such as mercury from their systems. Autism, he said, could be the result.
But Dr. William Schaffner, professor and chairman of preventive medicine at Vanderbilt University in Nashville, Tenn., countered that this opinion demonstrates one of many hypotheses behind the development of autism in some children. Some of these hypotheses, he said, are being investigated. But none so far, he noted, have the weight of scientific proof.
"The theory, that there may be underlying genetic defect that results in or can be somehow activated by some environmental process or insult, and that this in turn leads by some biological mechanism to autism is a valid theory, and it is a theory being pursued by the autism research community," Schaffner said.
"But any subset of this theory is a hypothesis, and you don't draw conclusions from a hypothesis."
The case follows a legal ruling in early March in which a special master appointed by the U.S. Court of Federal Claims determined that the family of 9-year-old Hannah Poling of Athens, Ga.. was entitled to receive an as yet undetermined award from the no-fault fund.
In this case, government health officials acknowledged that a vaccine, by worsening an underlying genetic condition, may have triggered autism-like symptoms in the girl. But federal health authorities at the time emphasized that the concession should not be interpreted to mean that vaccines cause autism.