A Randomized Trial of Two Coverage Targets for Mass Treatment with Azithromycin for Trachoma

Background: The World Health Organization recommends at least 3 annual antibiotic mass drug administrations (MDA) where the prevalence of trachoma is >10% in children ages 1-9 years, with coverage at least at 80%. However, the additional value of higher coverage targeted at children with multiple rounds is unknown. Trial Design: 2x2 factorial community randomized, double blind, trial. Trial methods: 32 communities with prevalence of trachoma >= 20% were randomized to: annual MDA aiming for coverage of children between 80%-90% (usual target) versus aiming for coverage>90% (enhanced target); and to: MDA for three years versus a rule of cessation of MDA early if the estimated prevalence of ocular C. trachomatis infection was less than 5%. The primary outcome was the community prevalence of infection with C. trachomatis at 36 months. Results: Over the trial's course, no community met the MDA cessation rule, so all communities had the full 3 rounds of MDA. At 36 months, there was no significant difference in the prevalence of infection, 4.0 versus 5.4 (mean adjusted difference = 1.4%, 95% CI = -1.0% to 3.8%), nor in the prevalence of trachoma, 6.1 versus 9.0 (mean adjusted difference = 2.6%, 95% CI = -0.3% to 5.3%) comparing the usual target to the enhanced target group. There was no difference if analyzed using coverage as a continuous variable. Conclusion: In communities that had pre-treatment prevalence of follicular trachoma of 20% or greater, there is no evidence that MDA can be stopped before 3 annual rounds, even with high coverage. Increasing coverage in children above 90% does not appear to confer additional benefit.