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Independents' Day

Can thiomersal be linked to autism?

QA patient recently came to see me bearing an article from the Daily Telegraph suggesting mercury in the DTP vaccine could be a trigger for autism. Could it?

AConcern over thiomersal in childhood vaccines relates to the fact that it contains a mercury derivative ­ ethylmercury.

It is known mercury in high doses may cause brain damage, but the low levels in vaccines have not been shown to be associated with such effects.

Infant vaccines that contain thiomersal are diphtheria, tetanus and whole-cell pertussis (DTwP), diphtheria and tetanus for children (DT) and tetanus and low-dose diphtheria (Td).

A recent review by the UK Committee on Safety of Medicines concluded there was no evidence that thiomersal-containing vaccines caused neurodevelopmental problems. Two independent UK epidemiological studies of the safety of thiomersal-containing vaccines in infants showed no developmental effects.

A further study in infants has shown that ethylmercury is rapidly excreted.

The US research by Geier and Geier referred to in the Daily Telegraph has been condemned for its methodology using data from the US Adverse Event Reporting System.

The UK's Medicines and Healthcare Products Regulatory Agency has pointed out that 'the results of this study cannot be used to draw any conclusions on the association between

DTP vaccine and the development of autism, cerebellar ataxia, mental retardation and permanent brain damage'.

Experts advise that the benefits of vaccination far outweigh the risks, if any, of exposure to thiomersal.

Dr George Kassianos is a GP in Bracknell, Berkshire, and an RCGP spokesperson on immunisation

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