Impact of annual targeted treatment on infectious trachoma and susceptibility to reinfection

Context The World Health Organization developed the SAFE strategy ( Surgery for trichiasis; Antibiotics for Chlamydia trachomatis infection; Facial cleanliness; and Environmental improvement) to eliminate blinding trachoma globally by the year 2020. Despite a number of studies using various intervals of treatment for different prevalence rates, there has been a lack of sufficient follow-up beyond the final treatment point to determine rates of recurrence of disease and infection and the risk factors that may contribute to each. Objective To evaluate the impact of 2 annual targeted azithromycin treatments on active trachoma and C trachomatis infection rates over 3 years in Vietnam. Design, Setting, and Participants Three communes were randomly selected for a longitudinal study in Vietnam from November 2000 through November 2003. Individuals (n = 3186) were graded for trachoma followed by conjunctival sampling to detect chlamydiae by commercial polymerase chain reaction. Grading and chlamydial detection were repeated every 6 months for 3 years. Intervention Azithromycin was given to children aged 5 through 15 years with active trachoma and their household members in SAFE and SA communes at baseline and 12 months; these communes were compared with the S-only control commune that did not receive azithromycin targeted treatment. Main Outcome Measures Prevalence and incidence of active trachoma and C trachomatis infection in all communes at baseline, 6, 12, 18, 24, and 36 months. Subgroup analysis evaluated new infection, continuing infection, and reinfection at 6, 12, 18, 24, and 36 months and risk factors for each. Results Reinfection rates increased significantly between 12 and 36 months for SAFE ( from 1.6 to 29.3 per 1000; P < .001) and SA (5.1 to 25.3 per 1000; P = . 002) communes but not for the S-only commune (13.4 to 6.7 per 1000; P = .55) after 24 months. Compared with the S-only commune, mixed-effects and generalized estimating equations ( GEE) logistic models showed that reinfection risk was significantly higher for SAFE ( odds ratio [OR], 4.1; 95% confidence interval [CI], 1.5- 9.8; P = .005) and SA ( OR, 4.2; 95% CI, 1.1-17.3; P = .04) communes at 36 months. Conclusions Increasing reinfection rates suggest that treatment may interrupt the duration of infection required for developing immunity, increasing the number of individuals susceptible to reinfection and adversely affecting disease prevalence over time. Additional research is needed to determine optimal trachoma control strategies, including evaluation of the "F" and "E" components.