Measles monster in the making

Once there was talk of eradicating measles. Yet for now the World Health Organisation is aiming only to cut deaths by half. But virologists warn that measles could stage a murderous comeback if we do not vaccinate more of the world' p soon.< children s>

In poor countries where vaccination is limited, measles is still a big killer, of children especially. Nearly a million people die of the disease every year and survivors may be left with permanent brain damage. In 1990, the UN called for 90 per cent of the world's children to be vaccinated against measles by 2000. Though vaccination costs just 26 cents, the figure is still only 75 per cent.

Only three years ago the WHO hoped measles would follow smallpox into oblivion. Yet this month it launched a campaign with a more modest aim--to cut the death toll in half by 2005.

Because vaccination produces a more limited immune response than infection, vaccinated people are more likely to harbour the virus sub-clinically than those who've had the disease. So if vaccination is rapidly expanded in a country, when cases of measles stop many people will be immune because they've actually had measles. This makes it less likely that measles will circulate subclinically.

If health officials are slow to vaccinate, however, by the time measles is eliminated most people will only have the limited immunity induced by vaccination. That makes it more likely the virus will circulate unnoticed--and that's dangerous. The more this happens, the greater the chance a resistant strain will emerge and make even vaccinated people sick.

Item provided courtesy of New Scientist