After testing on more than 800,000 children in Malawi, Ghana and Kenya, the WHO has recommended the use of a vaccine against malaria, a disease that kills nearly 400,000 people every year, mostly children under five. The jab is effective against one of the parasites that transmits the disease and reduces the risk of severe cases by 30 percent, which is enough to save tens of thousands of lives. Associated with other methods, it could drastically reduce the number of sick people each year. Could it even contain the epidemic? Our correspondents report.