Doctors Argue Against Proposed Ban On Vaccine Preservative

Dec 16, 2012
Originally published on December 17, 2012 3:55 am

An old complaint about the safety of childhood vaccines is finding new life at the United Nations.

The U.N. Environment Program is considering a ban on thimerosal, a vaccine preservative that is widely used in developing countries. The program expects to make a decision sometime after a final meeting on the issue in January.

Thimerosal, which contains a form of mercury, was removed from most childhood vaccines in the U.S. and Europe more than a decade ago, amid public fear that it could cause autism. Several large studies later found no risk from the preservative and that removing it did nothing to change autism rates.

Now the proposal before the U.N. has public health officials once again trying to reassure people that thimerosal is safe. Three separate papers in the journal Pediatrics argue against an international ban.

"This is critical," says Dr. Walter Orenstein of the Emory Vaccine Center at Emory University, and an author of one of the papers. "Lives potentially would be lost if we banned thimerosal from vaccines."

Thimerosal keeps vaccines from going bad in parts of the world where other options, such as refrigeration or single-dose vials, aren't practical.

The proposed ban is part of a larger effort to reduce exposure to mercury, which can affect brain development. And public health experts strongly support most aspects of that effort, Orenstein says.

"But when it comes to thimerosal in vaccines, the benefits far outweigh any risks," he says, adding that a ban could mean the return of diseases that used to kill millions of children each year in developing countries.

"Pertussis or whooping cough could really resurge in these areas," Orenstein says.

But Orenstein and other experts weren't always so certain about thimerosal. In 1999, they asked vaccine makers in the U.S. to stop using the preservative in childhood vaccines.

At the time, some parents of children with autism were alleging that the thimerosal in vaccines caused the disorder. Also, researchers realized that some children could be getting more mercury from vaccines than the Environmental Protection Agency deemed safe.

So Orenstein says he and others erred on the side of caution.

"At the time, we just didn't know what the toxic effects might be or might not be," he says. "And one of our concerns was, what if we did the studies and three years later found there was harm?"

The studies showed just the opposite, though. And scientists also determined that the form of ethyl mercury in thimerosal is far less dangerous than methyl mercury, the form found in seafood. So the EPA exposure limits didn't really apply.

But groups opposed to thimerosal say they're not convinced by the studies. And they say it's wrong to give the preservative to children in developing countries, but not to children in the U.S. and Europe.

The practice is "egregious, offensive and unacceptable," says Eric Uram, executive director of the U.S.-based group SafeMinds.

SafeMinds has played a prominent role in pushing for the international ban. But so far, countries that might be affected by it have been less vocal.

Uram says SafeMinds has contacted officials from countries including Nigeria and Uganda and found they are concerned. But he says they are hesitant to speak up because the World Health Organization has deemed thimerosal safe.

"They defer to WHO for guidance on health issues," he says. "So it becomes inappropriate for them to say that the WHO is incorrect."

Uram also disagrees with public health officials who believe the ban would disrupt vaccination programs in developing countries. The ban would be phased in, he says, giving countries time to find alternatives to thimerosal.

But right now there is no good alternative, says Heidi Larson of the London School of Hygiene and Tropical Medicine. In the U.S., she says, most childhood vaccines are packaged in single-dose vials, which don't need a preservative. That drives up the cost of each dose and makes it more difficult to transport large amounts of vaccine, she says.

Also, Larson says, there is no scientific reason to ban thimerosal from vaccines. "It would be bowing to public pressure," she says.

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DAVID GREENE, HOST:

And we're going to consider now another aspect of childhood health. An old complaint about the safety of childhood vaccines is finding new life at the United Nations. A branch of the U.N. is considering a ban on a vaccine preservative that is widely used in developing countries. This preservative contains a form of mercury.

NPR's Jon Hamilton reports it was removed from most childhood vaccines in the U.S. and Europe more than a decade ago, despite a raft of studies that found no risk.

JON HAMILTON, BYLINE: The preservative is called thimerosal and it keeps vaccines from going bad in parts of the world where other options, like refrigeration, would be difficult.

Walter Orenstein is from the Emory Vaccine Center at Emory University.

WALTER ORENSTEIN: Lives potentially would be lost if we banned thimerosal from vaccines.

HAMILTON: The proposed ban is part of a larger effort to reduce exposure to mercury, which can affect brain development. Orenstein says public health officials support most aspects of that effort.

ORENSTEIN: But when it comes to thimerosal in vaccines, which protect the vaccine supply in developing countries, the benefits of that far outweigh any risk.

HAMILTON: Orenstein helped write one of three papers in the journal Pediatrics that support continued use of the preservative. He says a ban could mean the return of diseases that used to kill millions of children each year in developing countries.

ORENSTEIN: Pertussis or whooping cough could really resurge in these areas. An organism called Haemophilus influenza type B, or Hib, which causes severe meningitis and pneumonia, that would resurge; Hepatitis B could go way up.

Orenstein wasn't always so sure about thimerosal. In 1999 he and many other experts asked vaccine makers in the U.S. to stop using the preservative in childhood vaccines. The move came amid public fears that vaccination could cause autism. There was also evidence that some children could get more mercury in vaccines than the EPA recommends. So Orenstein says he and others erred on the side of caution.

At the time we just didn't know what the toxic effects might be or might not be. And one of our concerns was: What if we did the studies and three years later found there was harm? Since that time, many, many studies have been done and we've learned a lot.

HAMILTON: Big studies in the U.S. and Europe found no risk to kids. And scientists determined that the form of mercury in thimerosal is far less dangerous than the form found in, say, seafood. So the EPA exposure limits didn't really apply. Even so, vaccine makers kept thimerosal out of childhood vaccines in the U.S. and Europe. And now, groups that still see a link between mercury exposure and autism are saying it's wrong to take a different approach in other countries.

Eric Uram is with the U.S. group SafeMinds.

ERIC URAM: SafeMinds saw this as an egregious, offensive and unacceptable outcome that was being foisted onto the developing world.

HAMILTON: Uram says his group contacted officials from countries including Nigeria and Uganda and found that they are worried. But he says they are hesitant to speak up because the World Health Organization has deemed thimerosal safe.

URAM: They defer to WHO for guidance on health issues. So it becomes inappropriate for them to say that the WHO is incorrect.

HAMILTON: Uram also says the proposed ban would not disrupt existing vaccine programs.

URAM: We support an eventual ban. We look at a phase-out. We're not saying that we should just flip a switch.

HAMILTON: The United Nations Environment Program expects to make a decision about the ban next year.

Jon Hamilton, NPR News. Transcript provided by NPR, Copyright NPR.