SAN FRANCISCO, Nov. 1 (UPI) -- Two independent researchers who gained entry to an immunization-information repository used by government scientists to clear vaccines of blame in the rise of autism diagnoses came up with strikingly different conclusions.
Challenging the status quo were Dr. Mark Geier, president of Genetic Centers of America who has studied immunization safety issues for 30 years and testified as an expert witness in dozens of vaccine-injury cases, and his son David, president of MedCon Inc., a medical-legal consulting firm.
In comparing records of children who received a diphtheria-tetanus-pertussis shot preserved with a mercury-containing compound called thimerosal with those who got a thimerosal-free version, they reported the former faced increased risk for speech impairments, autism and attention-deficit disorder -- a risk they said rose along with the level of mercury exposure.
Two years later, using the same information source, the duo -- whose work forms a staple of anti-thimerosal arguments -- linked mercury in vaccines to unspecified developmental delay, tics, attention-deficit disorder, language and speech problems, and neurodevelopmental irregularities in general.
In another survey the Geiers calculated children receiving thimerosal-containing shots were two to six times more likely to have autism, mental retardation and speech disorders than were those not exposed to the mercury-based compound.
In a series of additional investigations, they also reported connecting thimerosal exposure to heart problems, personality disorders and thinking abnormality.
These studies were largely based on complaints made to the Vaccine Adverse Event Reporting System, a cooperative program of the Centers for Disease Control and Prevention and the Food and Drug Administration that scientists say only loosely serves as a mirror to real-life trends.
Information coming from the network is considered a wild card in research because the reporting is voluntary, representing no more than an estimated 10 percent to 20 percent of actual cases, and unrestricted, meaning anyone can call in any ailment he or she deems vaccine-related, said Dr. Ben Schwartz, senior science adviser in the National Vaccine Program Office of the Department of Health and Human Services in Washington.
In each paper, the Geiers cautioned against the potential dangers of thimerosal and called for its removal from all childhood medicines.
Another population-based analysis that pointed to an autism-mercury link, this one unpublished, came from Mark Blaxill, a Massachusetts-based consultant, father of a daughter with autism and board member of the anti-mercury group SafeMinds.
The medical mainstream majority has shrugged off all these findings, taking issue with how the studies were constructed, conducted and concluded, and deeming them no match for the massive investigations at major academic centers that, taken together, have involved hundreds of thousands of children in several countries without finding a thimerosal link to autism.
As the ultimate established authority, the Institute of Medicine of the National Academy of Sciences dismissed the immunization-implicating studies as "uninformative" or "uninterpretable" due to poor design and methods.
The panel did deem "provocative" -- and urged more research into -- clues pointing to biological mechanisms underlying autism, including experiments showing thimerosal's effects on the biochemistry of cells and indicating abnormalities in the immune system or metal metabolism in people with autism.
What has largely escaped public notice is that while these experts saw no scientific evidence of a relationship between vaccines or thimerosal and autism, they nevertheless conceded that with the causes of autism still a mystery, they "cannot rule out, based on the epidemiological evidence, the possibility that vaccines contribute to autism in some small subset or very unusual circumstances."
In fact, some suggestive results along these lines have come to light since the report was published.
For one, a team of cell biologists, toxicologists and molecular bioscientists at the University of California, Davis, has found in mouse studies that so-called dendritic cells -- which play a crucial role in coordinating the body's attack against viruses, bacteria and other foreign invaders -- show an ultra-sensitivity to thimerosal that could impair the disease-fighting immune system's ability to respond to potential health threats.
In the lab-dish experiments, the mercury-based preservative, in amounts equivalent to those once commonly found in childhood vaccines, altered the normal function of these cells, each of which can order up to 300 "foot soldier" molecules to conduct search-and-destroy missions when the immune system is under attack.
Although the results are compatible with the theory that mercury in medicines can lead to neurodevelopmental problems, the study authors caution against jumping to such conclusions.
The findings do not directly implicate thimerosal in disorders such as autism, the researchers emphasize. For one thing, the investigators say they do not know whether the mouse findings are applicable to humans, a question they will explore next.
Some scientists speculate that while not causing autism, vaccines may provide a trigger for it in certain cases.
"It is possible for a small portion of children something like an injection or bad reaction to it could trigger the onset of autism, could be the precipitating event of a disorder that would occur anyway, like juvenile diabetes, that is not present at birth but emerges later," said Steven Gutstein, psychologist, autism specialist, academic researcher and child, marital and family therapist.
He also is co-director of The Connections Center for Family and Personal Development and the Relationship Development Research Institute in Houston, and author of "Autism Aspergers: Solving the Relationship Puzzle" (Future Horizons Inc., 2000), a treatise on the method he developed to teach social skills to individuals with autism spectrum disorders.
"People get confused in autism between vaccines maybe as a precipitating event in a percentage of (children) and the idea that it would actually cause autism," he said. "That would have to be a strange occurrence."
Not so strange to those who are convinced that, perhaps due to some genetic glitch, certain youngsters have problems flushing mercury from their bodies in the way healthy individuals do, and that vaccines provide a pathway for the neurotoxin to arrive at and accumulate in their brain, leading to neurological problems.
In a study compatible with that viewpoint, researchers found a genetically susceptible strain of rodents developed autistic-like behavior when given thimerosal at a level roughly proportional to what infants once received in many vaccines and still do in some flu and booster shots.
They observed three of four groups of young rats getting the injection showed no effects, but the fourth -- the one with a hereditary sensitivity to mercury -- had delayed growth, social withdrawal, brain abnormalities and bizarre behaviors, with one animal eating through the cranium of his cellmate.
The experiments raised questions about whether some people might likewise be born with a vulnerability to thimerosal's effects.
"These findings implicate genetic influences and provide a model for investigating thimerosal-related neurotoxicity," the study authors concluded.
Next: Compelling clues emerge from research
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