Among the more than one million people malaria kills annually are hundreds of thousands of children. Most are under age five, their immature immune systems failing to control the aggressive disease. The majority of these children are from the developing world. Almost 90 percent are from sub-Saharan Africa. Killing children is not all malaria does. Economically, malaria drains the wealth of nations and households. Recently W.H.O. reported that malaria costs Africa alone $12 billion a year.