The primary analysis, pairwise comparisons of attack rates, will be made between each intervention group using the Student’s t test, weighted to account for varying cluster size, and following an intention-to-treat basis. If the assumption of normality does not hold, we will consider a transformation of the data or a non-parametric test such as the Wilcoxon rank-sum test. Attack rates in each arm will be expressed as a weighted mean of cluster-specific attack rates, and will be presented with their 95% confidence intervals. Each of the two intervention groups will be independently compared to the standard care arm. The overall effect of prophylaxis in the intervention arms will be calculated as OEP = (AR0 – AR1)/AR0, where AR0 and AR1 are the weighted average attack rates in the control and treatment arm respectively . The direct effect of ciprofloxacin prophylaxis will be estimated by comparing attack rates among persons receiving ciprofloxacin versus those not receiving ciprofloxacin in the household-prophylaxis arm.