Additional file 2 presents simulations of the number of clusters necessary given specified attack rates and impact of the ciprofloxacin intervention, assuming an alpha (α) error of 5%, 90% power, and an inter-cluster correlation coefficient of 0.025 [22, 23]. The most likely parameters would need less than 75 villages per arm, which is historically a reasonable number of villages affected in meningitis outbreaks in HDs in Niger and in neighboring countries in the meningitis belt.