Trachoma, an ocular infection caused by C. trachomatis, is the second leading infectious cause of blindness worldwide. Years of repeated infection with C. trachomatis cause the eyelid to scar and contract and ultimately to rotate inward such that the eyelashes rub against the eyeball and abrade the cornea (trichiasis). The World Health Organization (WHO) has endorsed a multi-faceted strategy to combat trachoma, which includes the use of antibiotic treatment to reduce the community pool of infection with C. trachomatis. The objective of this study is to conduct a randomized, community-based trial in three countries (Niger, Tanzania and The Gambia), representing different baseline endemicities, of alternative coverages and frequencies of administration of mass antibiotic treatment as well as to determine the cost-effectiveness of these different strategies from a program perspective.

A randomized, 2x2 factorial designed trial will be implemented in each of the three countries. Communities will be randomized to two different coverage targets (80%-89% versus ≥90%) for three years of mass treatment.

In The Gambia and Tanzania, communities will be further randomized to yearly mass treatment versus mass treatment at baseline followed by yearly mass treatment only if trachoma prevalence in sentinel children is greater than 5%. The communities will continue to be followed and treatment will resume if trachoma prevalence is found to be 20% or greater at the 12 or 18 month surveys.

In Niger, communities will be randomized to the different coverage levels for annual mass azithromycin distribution and further randomized to biannual treatment at the two coverage targets for children ages twelve or younger.

Cross-sectional rates of trachoma and infection will be determined by examining sentinel children, age five years or younger, randomly selected from each community based on a community census. The census will be updated each year, and villages will be monitored at baseline, 6, 12, 18, 24, 30, and 36 months for infection and clinical disease.

The three-year study is in accord with the WHO guidelines which recommend three years of annual mass treatment followed by a re-survey to determine need for further treatment. The investigators will evaluate the efficacy of guiding further mass treatment according to a laboratory test for Chlamydia or WHO guidelines. Where investigators estimate communities have infection rates less than 5% in sentinel children, or trachomatous inflammation (TF) ( rates less than 5%, the community will be "graduated" from further mass treatment and followed for up to three years to look for evidence of re-emergent infection and disease. If rates of infection are found to be 20% or more return at the 12 or 18 month survey, mass treatment will be re-initiated.

Inclusion criteria for communities:

• Communities are located in the target districts and accessible by vehicle
• The community leaders consent to have the community enrolled
• Rapid assessment and/or available data suggest trachoma rates are higher than 20% in the community.
• The community size is <5,000 persons or >250 persons.

If a community meets the inclusion criteria and community leaders consent to have the community enrolled, then sentinel children will be selected based on the following criteria:

• The child is age 5 years or younger
• The child must be a resident in an eligible, sample community (defined as either living in the community since birth, or moved in with parents or guardians).
• The child must not have an ocular condition that would preclude grading trachoma or taking an ocular specimen.
• The child must be willing to have a swab taken as part of being a sentinel child (this is critical for The Gambia and Tanzania, as each swab result counts towards meeting the stopping rule)
• The child must have an identifiable guardian capable of providing consent to participate.

For the final analysis the main effect of stop rule was not considered in Tanzania since no communities had prevalence < 5%.Only the main effect of coverage was analyzed there.

In Gambia and Niger stop rule was applied and analyzed along with the main effect of coverage.

3 years

Mass drug administration was done for all the communities in each branch. Adverse events were planned to be collected per community per arm.

No adverse event was reported in any community in all three countries.