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Children's Vaccines Health Center

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Did CDC Conspire to Hide Vaccine Risk?

'Simpsonwood Conspiracy' Claims Debunked; Concerns Remain

Early Concerns About Mercury continued...

To be on the safe side, vaccine makers agreed to remove thimerosal from vaccines as soon as possible. Single-dose vaccines are now thimerosal free (some may still have tiny traces of the compound), but no replacement yet has been found for thimerosal in the multi-dose vials.

Thimerosal is a mercury compound. Ironically, it has long been used to make vaccines safer. Tiny quantities of thimerosal kept vaccines free of dangerous germs that used to cause deadly infections in healthy children.

When researchers added up all the mercury in the infant vaccines, it was 40% greater than the amount of mercury the EPA considered a safe environmental exposure. This was a shock, recalls Christopher John Clements, MD, MPH, who then was an official with the World Health Organization's immunization program.

"I was the focal point for this issue in WHO," Clements tells WebMD. "I was as distressed as the CDC to discover that there was such a small body of scientific literature published on the chemical's safety, despite its having been used in vaccines for many years."

To be safe, the CDC, FDA, the American Academy of Pediatrics, and vaccine manufacturers in 1999 agreed to remove thimerosal from all vaccines as soon as possible. This was accomplished in 2001 (except for flu vaccine, now available in thimerosal-free formulations).

But what about children already exposed -- and what about ongoing exposure while thimerosal was being removed?

Thomas Verstraeten, MD, a Dutch researcher working at the CDC, designed and led a study that looked at data from two large California HMOs. He looked for a link between neurological and developmental disorders and thimerosal exposure in 124,170 infants.

And he did indeed see a red flag. Thimerosal appeared to increase children's risk of tics, neurodevelopmental delay, attention deficit hyperactivity disorder, and language delay -- not autism, but close enough for serious concern.

The data would be presented at the July 2000 meeting of the ACIP, a panel of experts that advises the CDC and FDA on vaccine policy. To prepare the vaccination community for the news -- and to figure out how to communicate Verstraeten's preliminary findings to the public -- the CDC held a June meeting to seek the advice of outside experts: 11 "consultants" and 49 "resource specialists."

Because of other meetings being held in Atlanta at the time, the CDC had to look outside the city for a venue. A suburban conference center was open: Simpsonwood.

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