09:53 PM PDT on Tuesday, June 28, 2005

From NBC and KING5.com Reports

The debate just won't die. The possibility of a link between the level of mercury used in childhood vaccines and autism has been going on for several years, with parents of autistic kids leading the way.

Many insist vaccines caused their children's autism.

Most scientists say it's simply not true.

The debate got a push in this month's Rolling Stone magazine, with an accusation that government researchers have known about a link for years.

Katherine LaBarre is among thousands of parents who are convinced that thimerosal is to blame. It's a mercury-based preservative used in children's vaccines in the 1990s.

Much of her 9-year-old son Pierre's childhood has been lost in the deep hole of anger, fear and heartbreak.

"Pierre was very afflicted. Tantrums, rolling on the floor, screaming, biting himself, banging his head… I refer to them as the dark years," she said.

Radio host Don Imus is giving the allegations air time and in this month's Rolling Stone magazine, Robert F. Kennedy Jr. alleges the government has suppressed evidence linking thimerosal to skyrocketing rates of autism.

"The science exonerating thimerosal is weak, is flimsy, and it's phony and it's fraudulent," he said.

Kennedy calls five major scientific studies that concluded there is no link "junk science."

But the Centers for Disease Control says nothing's been suppressed and there have been hundreds of studies.

"The overwhelming majority of scientific evidence that we have right now does not support the link between vaccines and autism. All of those studies have been peer reviewed, meaning facts were checked on those studies by independent reviewers," said Dr. Tanja Popovic, Acting Associate Director of Science, CDC.

But Sen. Joseph Lieberman is calling on the CDC to hand over its vaccination data to independent researchers for a new, in-depth study.

"Let's not have people concluding that there is a cover-up here when it comes to the health of the American children," he said.

The CDC says it will cooperate.

In 1999, thimerosal was eliminated as a preservative in childhood vaccines in the U.S., but trace amounts still exist, fueling criticism.

And while thimerosal is also being removed from the flu vaccine, which is administered to children and adults, parents and patients can only find out if their vaccine is thimerosal-free by asking their health-care provider.

Two states now ban it, 17 others are in the process of doing so.

But Minnesota immunization expert Kristen Ehressmann, herself the mother of an autistic child, says banning thimerosal is an over-reaction.

Health experts fear that all the talk about thimerosal will scare parents away from immunizing their children, even though thimerosal preservatives are no longer used.

Still, autism rates have continued to climb and because autism generally appears by age four, experts will monitor to see whether four years after thimerosal was removed as a preservative, those rates will soon start to decline.