Thimerosal - mercury: CDC's unspoken acceptance of vaccine additive raises furor

"There are all these concerns about mercury from these coal-powered plants and yet they kind of shrug their shoulders at mercury in the vaccines and frankly, I'm outraged," said Rep. Dave Weldon, R-Florida, one of the few members of Congress who also is a physician.

Officials with the federal Centers for Disease Control and Prevention said their goal is to protect against a serious illness that kills 36,000 Americans annually, including 143 children during the 2003-04 flu season.

The CDC took no stance on thimerosal, a mercury-based preservative, because there is no proof it harms children, officials said.

"There is a lack of scientific evidence that this really is a problem from the standpoint of any causal association with autism or (related) disorders," said Steve Cochi, acting director of CDC's National Immunization Program.

For years, many parents of autistic children have argued that vaccines triggered their children's disorder, even though many scientists dispute that idea.

Several thousand families have filed claims with the Vaccine Injury Compensation Program, which has yet to make a decision.

Vaccine makers have denied responsibility and insisted that thimerosal is safe.

In 1999, as a precautionary measure, the American Academy of Pediatrics and the U.S. Public Health Service urged drug companies to voluntarily remove thimerosal from children's vaccines.

Thimerosal, a compound that is 49.6 percent mercury by weight, has been used as a preservative in some vaccines and other pharmaceutical products since the 1930s.

Its purpose is to prevent fungal and bacterial contamination in multidose vials.

The recommendation for a voluntary removal came after scientists with the Food and Drug Administration determined that 6-month-olds who received the full recommended set of immunizations could accumulate doses of mercury that exceeded Environmental Protection Agency guidelines for their body weight.

Today, most childhood vaccines are thimerosal-free.

"The last lots of those childhood vaccines that still contained thimerosal expired a year ago January," Cochi said.

The flu vaccine will be the exception.

On Friday, the CDC recommended that children between the ages of 6 months and 23 months receive annual flu immunizations as part of the standard schedule.

As a result, hundreds of thousands of young children will get flu shots this fall.

The influenza vaccine is available with and without thimerosal, although the thimerosal variety greatly predominates.

The mercury-free version is more expensive, costing roughly $4 more per shot.

Cochi noted that thimerosal is made up of ethyl mercury, a different form than the methyl mercury that has triggered widespread government warnings about fish consumption and other types of exposure.

Scientists have done far more research on the impact of methyl mercury than ethyl mercury.

"The two chemicals do act very differently, with the methyl mercury tending to persist in fat tissues and remain in the body much longer and persist as a potential toxin," Cochi said.

National Institutes of Health studies "have shown that the very tiny dose of ethyl mercury that young children get in vaccinations is cleared very quickly by the body and the levels that are reached in the blood are well below what is considered to be the EPA threshold for concern," he added.

Others disagree, fearing that some scientists are rushing to judgment. Rick Rollens, the father of an autistic child and a cofounder of the M.I.N.D. Institute at UC Davis, said he fears vaccines may trigger autism in genetically vulnerable children.

Proponents of this theory believe some children do not excrete mercury as readily as others.

"We don't know, quite frankly, what is the toxic dose of mercury for the developing brain of newborns and young children, so it's totally irresponsible to slough this off as saying that a little bit of mercury is okay," Rollens said. "A little bit of poison is not okay."

Triggered by the CDC action, Rep. Weldon has introduced a bill that would require that the child flu vaccine contain no more than 1 microgram of mercury by Jan. 1, 2005.

His bill would phase out thimerosal in all vaccines, including those for adults, by 2007.

Supporters note that one study found that autistic children had lower levels of mercury in their hair than a control group, which might indicate they retained more and didn't excrete it as readily.

"I'm a conservative," Weldon said. "I'm not a liberal, left-wing, chicken-little-the-sky-is-falling sort of person. I've really tried to look at this fairly objectively and let the science run its course. But I've basically had it. I think we need a law that says you've got to get this out of vaccines."

In California, Assemblywoman Fran Pavley, D-Woodland Hills, has introduced a bill that would ban thimerosal-containing vaccines for children under age 3 and pregnant women as of Jan. 1, 2006.

Her measure, pending in the Assembly Appropriations Committee, would require makers of many other products to include mercury content on labels.

Such a move by California could help pressure vaccine manufacturers to produce greater quantities of thimerosal-free flu vaccine, she said.

Because of the time required to produce the flu vaccine, Cochi said, it's too late now for manufacturers to substantially increase thimerosal-free versions of the vaccine by this fall.

This year, there will be about 6 million to 8 million doses of the thimerosal-free version available out of 90 million to 100 million doses of flu vaccine nationwide, he said.

The CDC will buy as much as three-fourths of the available thimerosal-free doses for distribution to programs that immunize poor children.

Even if the CDC decided to mandate that all young children receive thimerosal-free shots this fall, there would not be adequate supplies, Cochi said.

The American Academy of Pediatrics, representing 57,000 physicians, supports the CDC decision not to take a stance on thimerosal in the flu vaccine.

The debate continues. About 10 states have bills pending that would ban thimerosal in childhood vaccines.

Barbara Loe Fisher, president of the National Vaccine Information Center, which promotes safer vaccines, said that with so little known about the causes of autism and the potential impacts of ethyl mercury, officials should adopt the stance of "when in doubt, do no harm."

But Cochi of the CDC said it would be bad policy for state lawmakers to act.

"I don't think this problem can be solved in the near-term by legislators," he said.