Preliminary results from the trial of a malaria vaccine show that it protected nearly half of the children who received it from bouts of serious malaria, scientists said Tuesday.

The vaccine, known as RTS,S and made by GlaxoSmithKline, has been in development for more than 25 years, initially for the U.S. military and now with most of its support from the Bill and Melinda Gates Foundation.

The early results

The clinical trial is scheduled to continue through 2014 and will include tests on more than 15,000 children, from infancy on up. Interim results released at a Seattle malaria conference Tuesday showed that three doses protected 56 per cent of the 6,000 children aged 5 months to 17 months. (The age group was chosen because newborns have some protection from their mother's antibodies.)

“The results are encouraging, but we still have a way to go,” said Dr. Tsiri Agbenyega, who heads malaria research at a Ghanaian hospital that was one of the 11 research sites.

He announced the results, which are being published in The New England Journal of Medicine.

While 56 per cent protection is not very effective, and most vaccines are not released until they do better than 90 per cent, Glaxo's chief executive, Andrew Witty, noted that even that much protection would save millions of lives over a decade.

Malaria is estimated to kill about 780,000 people a year, most of them African children. Adults who survive those childhood bouts usually develop at least partial immunity.

A few years ago the World Health Organisation estimated that malaria killed 1 million people a year, and in 2008 it said that mosquito nets, DDT and newer artemisinin-based drugs paid for by donor nations were making a dent.

But the estimates are controversial and change when new statistical methods are applied. Also, malaria can bounce back quickly as soon as control measures are relaxed or even in hotter, wetter weather.

It is far harder to make a vaccine against parasites like malaria than to make one against a virus. The malaria parasite changes shape as it moves from blood to liver and back to the blood, and each form has different surface proteins.

Many rivals

Many rival malaria vaccines, targeting different surface proteins or using different methods to provoke the immune system into a counterattack, are in development.

Some researchers have suggested combining several in one shot or giving sequential shots of different ones to see if combinations do better.

The field's most pessimistic experts argue that making a long-lasting malaria vaccine is impossible because even the “perfect natural vaccine” surviving repeated bouts of malaria fades away after a few years from the malarial area.

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