Scientists involved in the trial of a vaccine against malaria say they are optimistic they can defeat the disease. Early tests of the vaccine showed it could provide complete protection for some people.

Eighty five per cent of deaths are children under five years of age

The scientists have now launched trials in Kenya to see if the vaccine is as effective in the wider population.

There are over 300 million cases of malaria around the world each year and it claims more than one million lives.

More than 90 per cent of cases are reported in sub-Saharan Africa, where it is the main cause of death and a major threat to children.

There is currently no effective vaccine against the disease.

A malaria vaccine has eluded scientists not least because the parasite which carries the disease evolves rapidly and can become resistant to drugs.

To mark World Malaria Day,Al Jazeera's Catherine Soi reports from Siaya in western Kenya, part of Africa's so-called malaria belt, where doctors are conducting trials for a vaccine that promises to eradicate the disease once and for all.