Serology for trachoma surveillance after cessation of mass drug administration.

Background: Trachoma, caused by Chlamydia trachomatis (Ct), is the leading infectious cause of blindness worldwide. Yearly azithromycin mass drug administration (MDA) plays a central role in efforts to eliminate blinding trachoma as a public health problem. Programmatic decision-making is currently based on the prevalence of the clinical sign "trachomatous inflammation-follicular" (TF) in children.