Interventions.

An enumerative census was conducted to generate a list of all households in each study community. In the delayed intervention arm, communities received no azithromycin distribution for the 12-month period of the study. In the annual and single azithromycin distribution arms, a single mass azithromycin distribution was administered to all participants over 1 year of age. In the biannual distribution arm, 2 mass azithromycin distributions were administered to all individuals over 1 year of age. In the quarterly distribution arm, all children aged 1–10 years received 4 azithromycin distributions over the 12-month period. For azithromycin distributions, individuals aged 1 year and older received an oral, directly observed 20 mg/kg dose of azithromycin (up to 1 g in adults). Consistent with WHO policy at the time, children under 1 year of age and pregnant women were offered topical 1% tetracycline for 6 weeks, applied twice daily to both eyes and not directly observed. Ten-year old children received oral azithromycin in the quarterly arm, although only children 9 years and under were monitored for infection (0–9 years) and clinical activity (1–9 years, as follicles do not predictably appear before the age of 1 year). We pooled communities from the biennial distribution arm and the annual distribution arm for analyses in this report, as the intervention was identical over the 12-month period of the study.