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:2×2 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.