By Ben Hirschler

LONDON, Oct 17 (Reuters) - African babies -- the group most at risk of dying from malaria -- may be protected against the mosquito-borne disease by an experimental vaccine, researchers said on Wednesday.

The finding clears the way for final-stage testing of GlaxoSmithKine Plc's <GSK.L> shot and increases the chance that the world will have a usable vaccine within five years.

Malaria kills one person every 30 seconds, most of them young African children. Doctors believe a vaccine, given as part of routine infant immunisation, is the best hope in fighting the disease.

A clinical trial in Mozambique of 214 infants aged 10 to 18 weeks found the vaccine was safe and reduced new infections by 65 percent over a three-month period after treatment. Clinical illness was cut by 35 percent over six months.

Although such efficacy rates are not as good as for some childhood vaccinations, experts believe the huge burden of malaria means the new shot can still save millions of lives.

"This is a very major breakthrough," lead investigator Dr Pedro Alonso of the University of Barcelona told reporters in a conference call.

"These tantalising and unprecedented results further strengthen the vision that a vaccine may contribute to the reduction of the intolerable burden of disease and death caused by malaria."

ONE MILLION DEATHS A YEAR

Malaria, caused by a parasite carried by mosquitoes, kills more than 1 million people every year and makes 300 million seriously ill.

The latest findings, published online in the Lancet, are broadly in line with a 45 percent reduction in new infections reported in 2004 when Glaxo's vaccine, known as Mosquirix or RTS,S/AS02, was given to children aged 1- to 4-years old.

Mosquirix will now go into a large-scale Phase III trial in the second half of 2008, involving 16,000 infants and young children in seven African countries.

If all goes well, the vaccine -- which is the most advanced of a number in development -- will be submitted for regulatory approval in 2011, suggesting it could be commercially available in 2012.

Glaxo has promised to sell Mosquirix at low prices in developing countries. The exact price will be negotiated with purchasers, who are likely to be multilateral groups who would cover the cost on behalf of countries where malaria is endemic.

Glaxo has spent $300 million developing Mosquirix and expects to spend another $50 million to $100 million in future.

But the trials programme is also being financed by the nonprofit PATH Malaria Vaccine Initiative, helped by a $107 million grant from the Bill & Melinda Gates Foundation.

Mosquirix -- which is given in three doses -- targets just one stage in the malaria parasite's life cycle and its success has surprised some scientists, given the complexity of the disease.

The fact that it works suggests an improved vaccine, targeting multiple elements in the life cycle, might be even more effective.

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