TNFSF13B and Plasmodium vivax malaria: Although the statistical evidence supporting the described associations is limited by the relatively small sample size and, although it is impossible to tell whether the SNPs studied here are truly causal or are in LD with the causal variants, the results suggest that genetic variations in CD28 and interactions between polymorphisms in BLYS and CD28 may be involved in the control of the immune response against vivax malaria.