For decades, half of all childhood vaccines contained a chemical preservative called thimerosal.
It is made from mercury, one of the most poisonous substances on Earth.
News 8 has spent the past three months investigating claims that government regulators and some pharmaceutical companies knew of the dangers, but never told the public.
From the outset, it must be stressed that this report is not anti-vaccination. Every person interviewed for this story believes in the importance of having children immunized. Rather, the focus is on the possible link between thimerosal and neurological disorders.
Before the 1990s, 1 in 10,000 children were diagnosed with autism. But in the past decade, as the government has increased the number of mandatory vaccines, some recent studies suggest the rate of autism has risen to 1 in about 250 children.
So how much mercury are we talking about?
Approximately 12 out of the 18 vaccine doses the average American child receives before the age of two contain thimerosal. Cumulatively, that's more than 200 micrograms of mercury, which would fit on the head of a pin.
According to the EPA, dropping that pin-head of mercury into 23 gallons of water would make it unsafe for human consumption. "Think about the idea of injecting your own child with levels of mercury that are thirty to forty times what's considered safe for an adult," Dallas attorney Andy Waters said. "And, I think if any human being thinks about that very long, they recognize that this is something that never should have happened."
Dr. Boyd Haley is the Chairman of the Chemistry Department at the University of Kentucky. He's one of the nation's leading experts on mercury poisoning and has studied thimerosal in vaccines.
Thimerosal "is one of the most toxic compounds I know of," Haley said. "I can't think of anything that I know of is more lethal."
Two years ago, the Centers for Disease Control and Prevention conducted a study, which showed that three-month-old babies exposed to just 63 micrograms of mercury - less than half of the aforementioned pin top - were two-and-a-half times more likely to develop autism.
The study is stamped "Confidential" and "Do Not Copy or Release." Siegel says it was never made public because it was just a draft.
"Until they're final, and are ready for publication, they're always considered a draft, not to be widely distributed," Siegel said. "This preliminary information could be distributed, and that could do harm." So why was it marked 'Confidential, Do Not Release', rather than a simple 'Draft'?
Subsequently, the CDC did release a report to the public, but the findings were much different. The new study was amended with different data which lowered the autism rate.
Dr. Sidney Baker has reviewed both reports. Baker has authored six medical books, and written scores of articles on childhood behavior and autism.
Baker is critical of the CDC study.
"I can't imagine that smart people could possibly have re-arranged the data the way they were done, and represented the data the way they were done, without doing it on purpose and with the express purpose, as you say, of a coverup," Baker said.
Baker treats hundreds of autistic patients each year from around the country. He suspects that about half of the children he sees have been affected by thimerosal from their vaccines.
Baker said the CDC's refusal to release raw data from the study for outside experts to evaluate - a standard protocol in medical research - is helping to fuel the controversy.
Under pressure from the American Academy of Pediatrics and the CDC, pharmaceutical companies agreed to stop manufacturing vaccines containing thimerosal in March 2001. But while production may have ceased, vaccine vials already containing Thimerosal were not recalled.
A very simple solution for parents worried about upcoming shots for children is to ask your doctor ahead of time for thimerosal-free vaccines.
Thimerosal VSD Study - Phase I
FDA Thimerosal Report
CDC Thimerosal Information
Institute of Medicine - Thimerosal page
Autism Research Institute
Part 2 of this report
Vaccines That Contained Thimerosal
? DTaP: Tripedia (Pasteur Merieux Connaught), Acel-Immune (Wyeth-Ayerst),
Certiva (North American Vaccine)
? Td: All Products
? DTaP-Hib: TriHIBit (Aventis Pasteur)
? Hib: HibTITER multidose (Wyeth-Ayerst), ProHIBit (Aventis Pasteur)
? Hib/HepB: COMVAX (Merck)
? HepB: EngerixB (Glaxo-Smith Kline), RecombivaxHB (Merck)
Tips for Parents
Q: How can I be sure my child is receiving a thimerosal free vaccine?
A: Ask your pediatrician. If you are concerned your child's vaccine may contain thimerosal, call your doctor's office ahead of your child's scheduled visit and request Thimerosal-free inoculations. One sure sign of a thimerosal free vaccine is a single dose vial as opposed to a multi-dose vial.
Q: Do vaccines still contain thimerosal?
A: Beginning in March 2001, thimerosal was no longer added as a preservative to childhood vaccines though none were recalled. Some are still in circulation. You can also ask to see the vial and package insert to check for yourself.