Frequency of mass azithromycin distribution for ocular chlamydia in a trachoma endemic region of Ethiopia: a cluster randomized trial.

INTRODUCTION: Annual mass azithromycin distribution significantly reduces the prevalence of ocular Chlamydia trachomatis, the causative organism of trachoma. However, in some areas a decade or more of treatment has not controlled infection. Here, we compared multiple treatment arms from a community-randomized trial to evaluate whether increasing frequency of azithromycin distribution decreases prevalence in the short term. METHODS: Seventy-two communities in Goncha Seso Enesie Woreda in the Amhara Region of Northern Ethiopia were randomized to 1 of 6 azithromycin distribution strategies: 1) delayed, 2) annual, 3) biannual, 4) quarterly to children only, 5) biennial, or 6) biennial plus latrine promotion. We analyzed data from the 60 communities in the delayed, annual, biannual, quarterly, and biennial distribution arms at the 12-month study visit. Communities in the annual and biennial distribution arm were combined, as they each had a single distribution before any 12-month retreatment. We assessed the effect of increased frequency of azithromycin distribution on ocular chlamydia prevalence. RESULTS: Ocular chlamydia prevalence was significantly different across azithromycin distribution frequency in children (P<0.0001) and adults (P<0.0001), with lower prevalence associated with higher frequency. Among children, quarterly azithromycin distribution led to a significantly greater reduction in ocular chlamydia prevalence than the World Health Organization-recommended annual treatment prevalence (mean difference -11.4%, 95% CI -19.5 to -3.3%, P=0.007). CONCLUSIONS: Increased frequency of azithromycin distribution leads to decreased ocular chlamydia prevalence over a short-term period. In some regions with high levels of ocular chlamydia prevalence, additional azithromycin distributions may help achieve local elimination of infection.