Slow resolution of clinically active trachoma following successful mass antibiotic treatments.

T rachoma, caused by infection with ocular strains of chlamydia, is the leading infectious cause of blindness worldwide. The World Health Organization recommends that in districts where the prevalence of clinically active trachoma exceeds 10% in children aged 1 to 9 years, communities should receive 3 annual mass antibiotic distributions followed by clinical reassessment; any communities with persistent trachoma should continue receiving annual mass antibiotic treatments until the prevalence of clinically active trachoma in children aged 1 to 9 years falls below 5%. Although trachoma treatment decisions are based on the prevalence of clinically active trachoma, it is unclear how quickly the clinical signs of trachoma resolve once infection has been cleared, especially in areas with severe trachoma. We recently performed a series of clusterrandomized clinical trials for trachoma in an area of Ethiopia with hyperendemic trachoma. In these trials, infection was brought to a low level in 24 villages randomized to receive mass azithromycin treatments every 6 months. This provided an opportunity to determine the rate of resolution of the clinical signs of trachoma given little to no chlamydial reinfection.