Sample size Sample size is calculated based on the proportion of altered malaria antibody before and after intervention in arm 1 and arm 2. The seropositive prevalence rate used in the study is 50% (unpublished data), which is expected to be seronegative as much as 25% in arm 1; while the change in the arm 2 would be 10%. Sample size calculation is performed by WinPepi software assuming that the proportion of seroconversion (from + to -) is 25% in arm 1 and 10% in arm 2 (5% significance level, 80% power, and 1:1 sample size ratio). Required sample size would be 321 subjects. After considering design effect of 1.5, we will recruit 482 subjects per arm and this will be randomized from community blood collected sample.