The vaccine preservative contains mercury

During the 1990s, autism silently exploded across the United States, affecting up to 15 times as many children as it did in the prior decade.

A small but growing segment of the medical and scientific communities believes an additive included in mandated childhood vaccines is the agent that fueled the eruption.

But the medical mainstream, including national health agencies, refute that claim and question the motives of those who try to create a link between autism and vaccines.

At the center of the technical and complicated debate is thimerosal, a mercury-containing preservative that was removed from most vaccines after a 1999 recommendation by the Centers for Disease Control and Prevention and the Food and Drug Administration.

Studies by some scientists and physicians have shown that autistic children, because of certain genetic flaws, have difficulty excreting mercury from their bodies. Those studies haven't been enough to convince most of the medical community that thimerosal is to blame for the autism epidemic.

The CDC has its own studies and other independent studies to show there is not a link.

Both sides of the issue have claimed the other is motivated by money. The CDC, FDA and pharmaceutical companies could face billions of dollars in legal costs and settlements. The CDC also seeks to protect the integrity of the vaccine program.

Started in 1930s

Mercury, which the Department of Defense classifies as a hazardous material that could cause death if swallowed, inhaled or absorbed through the skin, found its way into vaccines in the 1930s through thimerosal.

Bacteria caused by needles re-entering vaccine vials containing multiple doses led to the death of several children when the U.S. government began expanding immunization programs. To prevent bacterial growth and extend vaccines' shelf life, thimerosal, nearly 50 percent mercury by weight, was added.

The preservative is only needed in multidose vials. Many vaccines are now contained in single-dose vials, so thimerosal isn't necessary.

The safety of thimerosal has been questioned from its introduction, but for decades the preservative served its purpose without causing major alarm. Then in the 1990s, immunization programs were expanded -- along with the amount of mercury-laced thimerosal that was being injected into children.

The parallel increase in autism diagnoses and immunizations soon led to theories of a connection.

The Environmental Protection Agency has established a safe limit of 0.01 micrograms of mercury per kilogram of body weight per day. Some vaccines, such as for hepatitis B, contained as much as 12.5 micrograms of mercury per dose up until the 1999 recommendation by the CDC and FDA.

EPA limits on mercury

With the hepatitis B vaccine, which is often given to newborns, an average 8-pound baby may have been injected with 78 times the EPA's daily exposure limit for mercury.

A 1999 FDA review acknowledged that children's exposure to mercury may have exceeded the EPA's limit but not limits established by four other health organizations, including the FDA. That review prompted a joint statement by the FDA and CDC that asked pharmaceutical companies to remove thimerosal from vaccines or reduce the amount of the preservative used in them.

"The question of thimerosal came up, and the FDA, for the first time, did some measurements," CDC spokesman Curtis Allen said. "The recommendation was made to ensure the confidence of the American people even though there was still no evidence at that time."

CDC officials say evidence is lacking five years later. Dr. Mark Geier, a Maryland geneticist and vaccinologist, along with his son and research partner, David Geier, say the CDC has chosen to ignore the science. Dr. Geier says about 5,000 articles have been published that at least question the safety of thimerosal in vaccines.

"This is about as proven an issue as you are ever going to see," Mark Geier said at a February meeting of an Institute of Medicine vaccine committee. "What is occurring here is a cover-up under the guise of protecting the vaccine program."

The Geiers have analyzed data and determined that the more thimerosal a child receives, the better his or her chances are of being autistic. The CDC says the Geiers misused information from a CDC database intended more for forming hypotheses than proving theories.

Conflict of interest

But some critics say the CDC shouldn't have a say in the matter.

"The primary conflict within the CDC is that they are responsible for promoting a billion-dollar vaccine promotion program while policing it to ensure safety at the same time," said Dr. David Weldon, a congressman and physician from Florida who is sponsoring a bill to ban thimerosal. "They are being asked to judge whether or not their promotion may cause harm to a small group of children. They should not be their own judges in this matter."

Weldon said more studies are needed by independent researchers with no conflict of interest.

At least one local parent doesn't need more studies to convince her of a link.

The image of two nurses simultaneously injecting multiple vaccine needles into her infant's legs haunts Melinda Clark of Parma, Mo.

She said she is "100 percent" certain that mercury caused her son's autism.

Her son, Nicholas, was born in 1996 and within 24 hours of his birth received the hepatitis B vaccine containing 12.5 micrograms of mercury.

"They warned me that he might have a slight fever or be crabby, but no one mentioned mercury, and it really angers me," Clark said. "If I had known that was in my baby's shot, I never would have allowed it."

Nicholas developed normally until age 2, when his vocabulary began regressing. He was diagnosed with autism at age 3. In 2002, Nicholas was tested for mercury poisoning. The tests showed a type of vitamin depletion that indicates mercury poisoning. "I had faith that I would be told about something like that in my son's vaccines," Clark said. "That still keeps me up at night."

Roger and Dena Petzoldt of Jackson stop short of saying vaccines caused their son's autism. But they believe the evidence at least suggests as much.

They had Ben tested for heavy metal poisoning and found he had high levels of mercury, lead, tin and other heavy metals.

Depending on when their child's symptoms began, other local parents have differing opinions on the thimerosal debate.

Debbie Scholl of Jackson says the vaccines likely did not affect her daughter, who was born with low muscle tone, a symptom of autism.

Spectrum of causes

Dr. David Crowe, a Cape Girardeau orthodontist whose son was diagnosed as autistic in 1985, thinks the vaccines may be responsible for a portion of the increase of autism but not all of it.

"I don't think you can say autism is caused by vaccines or any one thing," said Crowe, who has spent a good deal of his adult life researching autism. "Just like it's a spectrum disorder, there's probably a spectrum of reasons why it occurs."

Those who oppose the link between autism and thimerosal question why some children are affected while others are not. Researchers such as the Geiers point to a potentially fatal rash that afflicted numerous U.S. children during the 1940s.

The rash, known as pink disease, was eventually found to be caused by the mercury in a certain type of teething powder. Once the teething powder was taken off the market, pink disease disappeared.

In that instance, not every child exposed to the mercury-containing teething powder developed pink disease. Only a segment of the population was susceptible, and some scientists say that's exactly the case with autism and thimerosal.

Dr. Alan Clark, a physician from Carthage, Mo., is among the few doctors who are convinced that thimerosal is responsible for autism.

Clark, who administered vaccines for 30 years, feels betrayed that he was never told those vaccines contained mercury. Mercury has never been listed as an ingredient on vaccine vials.

He and his wife, Lujene, a former nurse, joined the nation's most vocal anti-mercury activists after their son was diagnosed with Asperger's syndrome, a form of autism, in 2003.

"It was hard for us to believe at first. In fact, I set out to disprove it," Lujene Clark said. "You assume that because the FDA has oversight that these vaccines would be safe, right? Wrong."