UN debates banning vaccine preservative – will health officials bow to public pressure or uphold sound scientific findings?

Posted: December 20, 2012 in Ethics, Events, Policy, Science

I knew that the US has an unwarranted fear against vaccines, but until I read a recent article in NRP’s Shots Blog, I didn’t realize that the United Nations (UN) has gotten mixed up in the vaccine debates also! Currently, the UN Environmental Program is considering a ban on thiomersal, a preservative used in vaccines around the world, especially in third world countries where single dose vaccines are not feasible. Ban of the preservative would have far-reaching consequences such as the return of deadly diseases and surges in childhood mortality rates. This is sadly the second time this week I have read about governmental bodies not following the advice of scientists who are basing their recommendations on sound, peer-reviewed science.

Thiomersal is an organomercury compound that has been commonly used as an antibacterial and antifungal agent since the 1930s. Organomercury compounds contain mercury, and this is where much of the anti-vaccine debates start, there, and the precautionary principle. The precautionary principle basically says ‘better to be safe than sorry.’ A mandated review of mercury containing foods and drugs by the FDA Modernization act of 1997 was conduced and the FDA, in collaboration with other groups, concluded that there was “no evidence of harm caused by doses of thiomersal found in vaccines, except for local hypersensitivity reactions.” Despite the lack of evidence that thiomersal was toxic, health experts were worried that overtime, levels of mercury in infants would surpass those set by the EPA and thus be potentially harmful. Therefore, due to the precautionary principle, thiomersal was removed from vaccines starting in 2001.

Unfortunately, in this case, the precautionary principle was wrong. The levels set by the EPA that health officials based their decision to remove thimerosal on were for methylmercury, the form of mercury found in seafood and that causes ‘mercury poisoning’. Thiomersal is broken down into ethylmercury, a substance that is cleared from the body at a much faster rate than methylmercury, thus using the EPA’s methylmercury levels to base the decision on was incorrect and an overestimation. The World Health Organization states, “The Global Advisory Committee on Vaccine Safety concludes that there is no evidence of toxicity in infants, children or adults exposed to thiomersal (containing ethyl mercury) in vaccines.”

Upon removing thiomersal in 2001, public health officials had hoped  the public’s trust in vaccines would increase, but instead, due to the apparent increasing rate of autism, various studies demonstrating the toxicity of methylmercury (not ethylmercury) exposure, and the increased number of vaccinations required for newborns and infants in the 1990s, many parents started to believe that there was a link between the mercury in thiomersal containing vaccines and autism. Add to this a few celebrity endorsements (Jenny McCarthy and Robert F. Kennedy, Jr.),  research papers supporting the hypothesis (that have been highly criticized for methodological problems and largely discredited), and the politicalization of the issue, and you have a widespread controversy with huge public health implications that is not backed by sound science.

Since the early 2000s, numerous additional studies have concluded that thiomersal is safe for use in vaccines. In 2004 the Institute for Medicine published a followup study that states, “Thus, based on this body of evidence, the committee concludes that the evidence favors rejection of a causal relationship between thimerosal-containing vaccines and autism” (bold in original publication). Additonally, numerous longterm epidemiological studies have also shown no link between thiomersal in vaccines and autism rates, and importantly, autism rates have continued to increase in the US despite the remove of thiomersal over ten years ago. To me, this is a classic example of ‘correlation does not equal causation,’ basically just becasuse two things are happening at the same time does not mean they are related or that one is the cause of the other.

Despite the scientific consensus on the safety of thiomersal in vaccines, there are still numerous anti-vaccine advocacy groups and parents who refuse to vaccinate their children. Luckily for the US and Europe, most vaccines come in single dose applications and thus do not require the use of a preservative such as thiomersal. Preservatives are needed when multiple doses are being taken from the same vial, such as is the practice in many third world countries where single dose applications are too cost prohibitive.

The UN Environment Program’s proposed ban, which is expected to be ruled upon in January, focuses on decreasing the levels of mercury around the world, and most of the proposal has support of health officials, as methymercury is a known neurotoxin. Where health officials do not agree with the UN proposal is when it comes to thiomersal. The NPR report reads, “”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 thiomersal from vaccines.”” Orenstein goes on to warn that diseases such as pertussis or whooping cough could easily make a resurgence in many areas of the world.

There is medical and scientific consensus that thiomersal is safe to use in vaccines, and as Heidi Larson of the London School of Hygiene and Tropical Medicine explains, if the UN were to ban this preservative, “”It would be bowing to public pressure,”” and to me that is not what public health policy should be based on!


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