Plasmodium falciparum rifin proteins, belonging to the largest known family of 
variable infected-erythrocyte surface-expressed proteins encoded by rif genes, 
were recently shown to be capable of inducing a strong immune response in P. 
falciparum-infected adults living in an area in Gabon where malaria is endemic. 
In the present study, the levels of antirifin antibodies were analyzed in serum 
obtained from 60 children from the same area who were admitted to hospital and 
diagnosed with severe malaria. High antirifin antibody concentrations in these 
individuals correlated significantly with their capacity to rapidly clear their 
parasites from the circulation after the start of chemotherapy. A doubling of 
antirifin antibody concentrations reduced the clearance time by 5 h (95% 
confidence interval, 4.1 to 6.9 h). In the same group of children, who were 
followed up for 2 years, antirifin antibody levels did not correlate with a 
reduced rate of reinfection or with a delay in the time to the first 
reinfection. However, the initial antirifin antibody levels were sustained over 
the study period. The likelihood that these antibodies could confer a certain 
degree of protection against malaria is supported by our findings of 
statistically higher levels of antirifin antibodies to all four rifin proteins 
in a group of 42 asymptomatic parasitemic children.