But Dr. Julie Gerberding, director of the U.S. Centers for Disease Control and Prevention, emphasized that the concession should not be interpreted to mean that vaccines cause autism.
"The government has made absolutely no statement about indicating that vaccines are the cause of autism, as this would be a complete mischaracterization of any of the science that we have at our disposal today," Gerberding said during a Thursday news conference. "I think we need to set the record straight on that."
And some vaccination experts said the legal rulings were an example of the courts taking action ahead of the evidence needed to justify such a move.
Still, on the steps of a U.S Federal Court in Atlanta Thursday morning, Athens, Ga., neurologist Dr. Jon Poling and his wife, Terry Poling, made it clear that they believed vaccines triggered the encephalitis that led to their 9-year-old daughter Hannah's autismlike symptoms.
"I wanted to know why my daughter, who had been completely normal until she received [five vaccines for nine different diseases], in one day was no longer there … no longer responding," Terry Poling told the crowd of reporters present.
The Polings said Hannah received the battery of vaccines in 2000, when she was 19 months old. Shortly after these shots, they said she suffered from a fever that left her screaming and arching her back. Following this, they said, Hannah began showing classic signs of autism — staring at lights, running in circles and staring at fans.
"When my husband saw this, his heart just broke," Terry Poling said.
But doctors overwhelmingly maintained that the case will have no effect on guidelines that urge parents to have their children vaccinated against disease. And they said that the fears spurred by this case could end up doing more harm than good to the nation's children.
They added that there is as yet no evidence providing a reliable link between vaccination and the worsening of underlying mitochondrial diseases such as the one suffered by Hannah Poling.
Dr. Pauline Filipek, associate professor of clinical pediatrics and neurology at the University of California Irvine School of Medicine, and her colleagues conduct research 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."
And vaccine experts said the victory for the Polings may represent a defeat for an important public health measure. Dr. William Schaffner, professor and chairman of preventive medicine at Vanderbilt University, said he believes the concession should not have been made until more evidence suggesting exactly how the vaccines may have contributed to Hannah's condition come to light.
"It appears that the judges in this case have not only made a legal decision but also a medical and scientific decision," he said. "I don't believe the court's role is to make these decisions."
"Legal action does not equate with proof," agreed Dr. Ira Rubin of Naperville Pediatrics in Naperville, Ill. "How many times have defendants in cases been found guilty and later found innocent when DNA testing is done?"
Does Compensation Mean a Connection?
This case, as well as other cases involving possible injury brought about by a vaccine, are handled under the National Childhood Vaccine Injury Act of 1986. The act created a no-fault system in which people with grievances, such as the Polings, would file injury claims against the federal government rather than sue the companies that made the vaccine or the health care providers who administered it.
A "special master" appointed by the U.S. Court of Federal Claims reviews these cases to determine whether vaccines were more likely the cause of the injury at hand. If the government chooses not to rebut the claim by showing that the vaccine probably was not responsible for the injury, the claim is approved and an award is made.
"But any subset of this theory is a hypothesis, and you don't draw conclusions from a hypothesis."
Dr. Gary Mirkin, CEO of Allied Pediatrics of New York in Great Neck, agreed.
"This case … looks like a child who had a very rare pre-existing, underlying condition that may or may not have been aggravated by the administration of multiple vaccines to result in a regressive form of autism or something that appeared to be autism," Mirkin said. "If this child had never had a vaccine, it is not inconceivable that the same scenario may have developed if the child was confronted with a serious infection or even a series of multiple infections."
Medical Recommendations Remain Unchanged
Schaffner said holding back on kids' vaccinations could expose them to risk of sickness or death from other conditions, including measles and polio.
"These diseases that affected childhood are now not known by this generation of parents, so there's no balancing of concern," he said.
"Without vaccination, these disease will return, and they will spread."
The legal standard set by this system is therefore a much lower bar than the demands of medical validity, which would require a much greater magnitude of evidence to draw the conclusion that vaccines were in any way responsible for an injury.
Regardless, the case has brought attention to the nearly 5,000 other families that lawyers have chosen in an effort to seek this compensation from the government, claiming that a mercury-based preservative in vaccines known as thimerosal brought about autism and other developmental disorders in their children. Since 2001, the ingredient has been absent from most vaccines, save for certain influenza shots.
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. Boyd Haley, a chemist at the University of Kentucky and vocal proponent of a vaccine-autism link, believes these 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 Schaffner 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.