SAN FRANCISCO, Sept. 15 (UPI) -- Now in full bloom among many parents and even scientists and doctors, the budding view of vaccine as agent of autism began sprouting in the 1980s.
It took firmer root in 1998 with the appearance of a widely publicized, highly suggestive study -- since then repudiated by the leading medical journal that published it and retracted for insufficient evidence by 10 of the 13 co-authors who wrote it.
The survey of 12 children, led by British gastroenterologist Dr. Andrew Wakefield, drew a link from the measles-mumps-rubella vaccine to bowel inflammation to autism.
Ironically, the MMR shot, which contains three weakened but live organisms that would be rendered ineffectual by thimerosal, has always been free of the mercury-based compound many critics view as the culprit in the rise of autism diagnoses over the past few decades.
Spurred by a public-pushed congressional mandate to study the mercury content in food and medicines, the Food and Drug Administration conducted a comprehensive assessment of the risk of thimerosal-preserved childhood vaccines.
The 1999 survey found no evidence of harm, other than some redness and swelling where the needle pricked the skin, the agency said.
However, along the way, federal researchers discovered that, depending on the vaccine's formulation and infant's weight, total mercury levels injected into some babies in the first six months of life -- a critical period for brain development -- surpassed the safety levels established by the Environmental Protection Agency.
Stressing it was purely a precautionary measure and standing by vaccines' safety, the Public Health Service (of which the FDA is a part), the Centers for Disease Control and Prevention, the Health Resources and Services Administration and the American Academy of Pediatrics promptly issued a recommendation for the removal of thimerosal from childhood shots.
At the time, the chemical was found in more than 30 vaccines, including several administered to infants.
These were permitted to remain in use until their shelf-life time ran out, meaning at least some likely would be around as late as November 2002 -- the FDA's estimated final expiration date for thimerosal-containing hepatitis B, Haemophilus influenzae type b and diphtheria-tetanus-pertussis inoculations.
This staggered withdrawal disappointed mercury opponents who not only wanted to see an immediate ban but also looked to a precise cutoff point as a basis for proving their prediction that once thimerosal exposure decreased, so would the autism caseload.
In any case, critics saw the move as too little too late.
By then, they argue, the thimerosal had set off an autism blowout by wreaking neurological havoc in a subset of children unable to excrete the poison or otherwise vulnerable to it.
Some speculate something else in vaccines -- aluminum, formaldehyde, even a hyper-reaction to the shot itself -- also might pose a risk.
"Autism is not a disease! It is a term from a psychiatric manual that describes people with bizarre behaviors," said Michael Wagnitz.
The senior chemist and trace-metal analyst in the Wisconsin State Lab of Hygiene at the University of Wisconsin in Madison is a volunteer at the thimerosal-opposing advocacy group Generation Rescue.
"Why do they act bizarre? Because their brains have been injured," he contended. "The amount of mercury that was injected into our children was 250 times higher than hazardous waste levels and hundreds of times higher than EPA consumption advisory levels."
Questions raised by some researchers about the scientific appropriateness of making such comparisons have failed to douse the ardor of the expanding ranks of mercury-in-medicine opponents who prefer to err on the side of safety.
A congressional subcommittee looking into the nation's vaccine policy sided with those sentiments.
"This epidemic in all probability may have been prevented or curtailed had the FDA not been asleep at the switch regarding the lack of safety data regarding injected thimerosal and the sharp rise of infant exposure to this known neurotoxin," admonished a staff report published in the Congressional Record in May 2003.
The incendiary implications fired up the smoldering controversy over the health effects of mercury exposure, which shows no signs of losing steam despite repeated reassurances by public health authorities and mainstream pediatricians that countless studies have shown no association.
Next: Implications of the vaccine debate.
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