Global elimination of trachoma: How frequently should we administer mass chemotherapy?

The World Health Organization has recommended repeat mass drug administrati on as part of their global initiative to eliminate blinding trachoma by the year 2020. The efficacy of repeat treatment will be tested empirically, bu t the results will not be available for many years, and recommendations for the necessary frequency of treatment are needed immediately. We have devel oped a mathematical model that uses available epidemiological data from a v ariety of countries. We recommend, based on our analysis, that in areas whe re trachoma is moderately prevalent (<35% in children), it should be treate d annually, but hyperendemic areas (>50% in children), it should be treated biannually.