Still, preventable diseases claim a high death toll in less developed countries. Mosquitoes have become resistant to common insecticides in some areas and international efforts to develop an effective vaccine against malaria have not yielded success. Several international public health initiatives in recent decades have focused on children. Many childhood diseases are preventable, and infant and childhood mortality can fall rapidly in a population once health initiatives that target these diseases are introduced. The percentage of children immunized against these six diseases increased from 20 percent in 1981 to about 80 percent by 1995.
Diarrhea is a leading health burden in many less developed countries.
International health agencies coordinated the training of health workers and mothers in how to administer ORT, which involves dissolving essential salts in clean water and feeding it to children suffering from diarrhea. ORT use was negligible in 1980, but it was used in an estimated 80 percent of diarrheal episodes by the 1990s, and had prevented millions of childhood deaths. 26 Infant and childhood mortality declined in many less developed countries between the 1970s and the 1990s. But diarrhea and the six target infectious diseases are still leading causes of disability and death in these countries. Immunization rates slipped in some countries during the late 1990s.