Field trials of malaria vaccines.

Malaria due to Plasmodium falciparum is probably the most important infectious disease in the tropical world. About 2000 million people live in areas exposed to malaria and 300 million individuals are infected every year. In Africa south of the Sahara alone, over 1 million children die annually as a result of malaria. It is a difficult parasitic disease both to diagnose and control. It does not provide sterile immunity even after long exposure periods. However, acquisition of partial immunity allows over 60 per cent of individuals with long exposure to carry the parasite in their blood without symptoms, posing difficulties for case definition, malaria attributable morbidity and deaths. Further, it is extremely difficult to establish the extent to which malaria has influence over the adverse outcome of other infectious disease like measles and malnutrition. The complex life cycle of the parasite involving human and vector mosquitos as well as its allelic diversity and antigenic variations makes the development and implementation of effective malaria control intervention problematic. It is now becoming evident that multi-intervention approach may be the most appropriate way of combating malaria in view of the increasing resistance of the parasite to antimalarial drugs as well as vector mosquitoes to insecticides. Malaria vaccines will therefore play a major role in future malaria interventions. New malaria vaccine candidates will require testing in malaria endemic countries. Sufficient sites for testing potential malaria vaccines must be prepared. In this paper we discuss the necessary preparations required for field testing of malaria vaccines in tropical countries.