Newspaper article International Herald Tribune

Stick with the Science

Newspaper article International Herald Tribune

Stick with the Science

Article excerpt

A blanket ban on mercury could block millions of needed vaccinations.

Government representatives are meeting in Geneva this week to decide whether to introduce a global ban on mercury that could include thiomersal, a mercury-based preservative that has been used in some vaccine manufacturing since the 1930s to prevent bacterial or fungal contamination of multidose vials of vaccine.

Hosted by the United Nations Environment Program, the intergovernmental negotiating committee is charged with drafting a global treaty to rid the world of the threats posed by mercury.

Despite the ominous connotations of mercury, the decision should in theory be a no-brainer: The scientific and medical consensus is that thiomersal poses no human health risk, and that rather than saving lives, a ban would put millions of the world's poorest children at risk of deadly diseases by disrupting vaccination programs.

But with vaccines, logic and evidence don't always prevail. In the late 1990s we were at a similar juncture when, as part of a broader remit to find ways to reduce the human health hazards posed by mercury and under pressure from anti-vaccine lobbyists, the U.S. Food and Drug Administration turned its attention to the safety of thiomersal (known in the U.S. as thimerosal).

Despite a lack of evidence that it was harmful -- and in the absence of any evidence to show that it wasn't -- the F.D.A. decided to take a precautionary approach and urged manufacturers to reduce or eliminate thiomersal from almost all vaccines in the United States.

Since then, scientists have published unequivocal evidence of its safety, including a 2006 study which showed that thiomersal is broken down by the body into ethylmercury. Unlike methylmercury, say from contaminated fish, which can make its way through the food chain and accumulate in the body, ethylmercury is naturally flushed out of the body within a couple of weeks. Despite such clinical and laboratory evidence, the damage to thiomersal's reputation had already been done, and anti-vaccine campaigners are still trying to fan the flames.

Anti-vaccination groups have long campaigned against the use of thiomersal, claiming that this organic mercury derivative was responsible for increases in developmental disorders such as autism. What's more, they argue that with a precautionary reduction already in place in the United States, denying children in developing countries access to the same thiomersal-free vaccines would be a global injustice.

Nothing could be further from the truth. Quite apart from the mountain of scientific evidence refuting any link between thiomersal and autism, with some studies involving hundreds of thousands of children, banning thiomersal or phasing out this agent would have a devastating impact on global health and lead to millions of children being denied access to life-saving vaccines. …

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