Randomised trial of SPf66 vaccine against Plasmodium falciparum malaria in children in southern Tanzania.

Malaria, especially that due to Plasmodium falciparum, is one of the most important parasitic disease in man. It causes more than 400 million cases per year and between 1 to 3 million deaths, mainly among young children and pregnant women in sub-Saharan Africa. The current malaria control strategies using rapid diagnosis and treatment as well as methods to reduce the man-vector contact have had limited success. In Kilombero district (Southern Tanzania), malaria transmission is perennial (parasite prevalence > or = 80% all year) and intense (approximatively 300 infectious bites per year). At the household level, each under-5 child suffers on average 3 clinical fever episodes per year. Minimum estimated community rates for serious malaria (cerebral malaria or malaria and anaemia) affect approximatively 5% of all children. Under conditions of a field experiment, the annual incidence of a febrile illness (axillary temperature > or = 37.5 degrees C) reported to the curative primary health services in each child was 0.86 of which 0,35 can be attributed to Plasmodium falciparum malaria. The best estimate of the SPf66 vaccine protective efficacy in the Kilombero was 31% (95% CI : 0.52).