American lawmakers initiate mercury probe for vaccines

By Gregory Roumeliotis

- Last updated on GMT

The US Congress has asked the country's National Institute of
Environmental Health Sciences (NIEHS) to conduct research on the
connection between vaccines containing mercury and neurological
disorders, further battering public confidence not just in the US
Centers for Disease Control and Prevention (CDC), but in vaccine
manufacturers as well.

The CDC has found no proof of a causal relationship between the use of thimerosal, a mercury-containing preservative in vaccines, and health threats to children, yet the use of vaccines with thimerosal was phased out in 1999 when the Public Health Service (PHS) and the American Academic of Pediatrics (AAP), under significant public pressure, asked for their voluntary withdrawal.

This was achieved by using single-dose instead of multi-dose vials, and although this offers an alternative to reducing the chance of bacterial contamination, it has increased the cost of manufacturing, storing and delivering vaccines and is partly blamed for intermittent shortages of vaccines in recent years.

Still, traces of thimerosal are present today in some flu vaccines administered to preschool children, and advocacy groups like the National Autism Association (NAA) are determined to take these vaccines off the market as well.

They also want the CDC investigated for "dereliction of responsibility"​ and accuse vaccine makers such as Merck of concealing knowledge about thimerosal's toxicity.

Vaccine manufacturers dispute this but their image is tainted with negative publicity they currently do not need; Merck has submitted an application for approval of a vaccine against the human papilloma virus (HPV), while GlaxoSmithKline is also developing an HPV vaccine.

Nevertheless, popular anger is mostly directed at the CDC at the moment for its perceived inertness, with prominent senator Joseph Lieberman and seven other politicians writing in a letter to the NIEHS that "if the federal government is going to have a study whose results will be broadly accepted, such a study cannot be led by the CDC."

They point to a sharp increase in the incidence of autism and other neurological disorders in the 1990s - though thimerosal was first used in the 1930s - and a recent peer-reviewed study of two government databases which shows that the incidence of childhood autism declined significantly between 2002 and 2005.

Irrespective of whether or not thimerosal is eventually proved to cause autism, John Bradley, a member of the AAP for 25 years who now sits on its committee on infectious diseases, told In-PharmaTechnologist.com​ he believes the AAP was responding to political pressure when it recommended the withdrawal of thimerosal.

"Politicians will go after anyone they can obviously but it is important to separate the science from the politics and even now there is not enough information available to categorically reach a conclusion on this, more studies are needed.

"Developing a new vaccine is already a risky business and the way this issue has been handled will make it even less attractive for drug companies to invest in vaccines."

Last week members of the European Parliament (MEPs) passed a non-binding resolution asking for an investigation into the health impact of ethyl mercury in vaccines "with a view to restriction of such use and a total ban."

The World Health Organisation (WHO) still uses vaccines with thimerosal in its vaccination programmes in the developing world - it says to not do so would be more expensive, thus denying millions of life-saving jabs.

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