Concerns about childhood vaccinations have centred on the health risks, and especially the possible link to autism. But the debate has overlooked an even more basic question: do the vaccines work in the first place?
A recent outbreak of chickenpox at a day-care centre in America among children who were all vaccinated suggests that more research needs to be done at this fundamental level.
The chickenpox (varicella) vaccine has been widely used in the USA since 1995, and UK health authorities are planning to introduce it as part of a new multi-vaccine in the next couple of years.
The few studies that have looked at the effectiveness of the varicella vaccine have come up with widely different conclusions about its effectiveness - anything from 100 per cent effective to just 71 per cent.
The outbreak at the day-care centre puts the scale way below this. Twenty-five children of the 88 attending the centre developed chickenpox over a 13-month period, despite being vaccinated. After allowing for shorter time periods, researchers worked out that the vaccine offered immunity in just 44 per cent of cases. (Source: New England Journal of Medicine, 2002; 347: 1909-15).
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