Characterizing trachoma elimination using serology.

Trachoma is targeted for global elimination as a public health problem by 2030. Measurement of IgG antibodies in children is being considered for surveillance and programmatic decision-making. There are currently no guidelines for applications of serology, which represents a generalizable problem in seroepidemiology and disease elimination. We collated Chlamydia trachomatis Pgp3 and CT694 IgG measurements (63,911 children ages 1-9 years) from 48 serosurveys, including surveys across Africa, Latin America, and the Pacific Islands to estimate population-level seroconversion rates (SCR) along a gradient of trachoma endemicity. We propose a novel, generalizable approach to estimate the probability that population C. trachomatis transmission is below levels requiring ongoing programmatic action, or conversely is above levels that indicate ongoing interventions are needed. We provide possible thresholds for SCR at a specified level of certainty and illustrate how the approach could be used to inform trachoma program decision-making using serology.
Competing Interests: KR, PJH, and PME are employees of, and EMHE receives salary support from, the International Trachoma Initiative, which receives an operating budget and research funds from Pfizer Inc., the manufacturers of Zithromax® (azithromycin). The other authors declare no competing interests. The authors alone are responsible for the views expressed in this article and they do not necessarily represent the views, decisions or policies of the institutions with which they are affiliated.