title: The efficacy of oral azithromycin in clearing ocular chlamydia: mathematical modeling from a community-randomized trachoma trial.
abstract: Mass oral azithromycin distributions have dramatically reduced the prevalence of the ocular strains of chlamydia that cause trachoma. Assessing efficacy of the antibiotic in an individual is important in planning trachoma elimination. However, the efficacy is difficult to estimate, because post-treatment laboratory testing may be complicated by nonviable organisms or reinfection. Here, we monitored ocular chlamydial infection twice a year in pre-school children in 32 communities as part of a cluster-randomized clinical trial in Tanzania (prevalence in children was lowered from 22.0% to 4.7% after 3-year of annual treatment). We used a mathematical transmission model to estimate the prevalence of infection immediately after treatment, and found the effective field efficacy of antibiotic in an individual to be 67.6% (95% CI: 56.5-75.1%) in this setting. Sensitivity analyses suggested that these results were not dependent on specific assumptions about the duration of infection. We found no evidence of decreased efficacy during the course of the trial. We estimated an 89% chance of elimination after 10 years of annual treatment with 95% coverage.
authors.affiliation: F.I. Proctor Foundation, University of California, San Francisco, CA, USA.
authors.forename: Fengchen
authors.initials: F
authors.lastname: Liu
authors.affiliation: F.I. Proctor Foundation, University of California, San Francisco, CA, USA; Department of Ophthalmology, University of California, San Francisco, CA, USA; Department of Epidemiology & Biostatistics, University of California, San Francisco, CA, USA. Electronic address: travis.porco@ucsf.edu.
authors.forename: Travis C
authors.initials: TC
authors.lastname: Porco
authors.affiliation: Kongwa Trachoma Project, Kongwa, Tanzania.
authors.forename: Harran A
authors.initials: HA
authors.lastname: Mkocha
authors.affiliation: Wilmer Eye Institute, Johns Hopkins Hospital, Baltimore, MD, USA.
authors.forename: Beatriz
authors.initials: B
authors.lastname: Muñoz
authors.affiliation: F.I. Proctor Foundation, University of California, San Francisco, CA, USA.
authors.forename: Kathryn J
authors.initials: KJ
authors.lastname: Ray
authors.affiliation: Faculty of Infectious and Tropical Diseases, Clinical Research Department, London School of Hygiene & Tropical and Medicine, London, UK.
authors.forename: Robin L
authors.initials: RL
authors.lastname: Bailey
authors.affiliation: F.I. Proctor Foundation, University of California, San Francisco, CA, USA; Department of Ophthalmology, University of California, San Francisco, CA, USA; Department of Epidemiology & Biostatistics, University of California, San Francisco, CA, USA; Institute for Global Health, University of California, San Francisco, CA, USA.
authors.forename: Thomas M
authors.initials: TM
authors.lastname: Lietman
authors.affiliation: Wilmer Eye Institute, Johns Hopkins Hospital, Baltimore, MD, USA.
authors.forename: Sheila K
authors.initials: SK
authors.lastname: West
mesh_terms: D000284:Administration, Oral; D000900:Anti-Bacterial Agents / Q000008:administration & dosage / Q000627:therapeutic use*; D017963:Azithromycin / Q000008:administration & dosage / Q000627:therapeutic use*; D002675:Child, Preschool; D016000:Cluster Analysis; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D008432:Mathematical Computing; D008962:Models, Theoretical; D015995:Prevalence; D012107:Research Design; D013636:Tanzania / Q000453:epidemiology; D014141:Trachoma / Q000188:drug therapy* / Q000453:epidemiology* / Q000635:transmission; D016896:Treatment Outcome
chemical_list: D000900:Anti-Bacterial Agents; D017963:Azithromycin
keywords: Azithromycin; Elimination; Mathematical model; SAFE strategy; Trachoma