• Community prevalence of trachoma and ocular C. trachomatis infection [ Time Frame: 5 years ] [ Designated as safety issue: No ]
  

• Community costs of mass treatment [ Time Frame: 5 years ] [ Designated as safety issue: No ]
  
• Community costs of incident infection [ Time Frame: 5 years ] [ Designated as safety issue: No ]
  
• Macrolide resistance in pneumococcus (% resistance over time, clustered by randomization unit) [ Time Frame: 36 months ] [ Designated as safety issue: No ]
  PRET Niger
  
  
• Anthropometric measurements (WHZ, WAZ, HAZ, MUACZ), as outlined by WHO child growth standards (0-5 years of age) [ Time Frame: 12-36 months after baseline ] [ Designated as safety issue: No ]
  PRET Niger
  
  
• Prevalence of anemia (hemoglobin levels in 0-5 year olds) and the prevalence of malaria [ Time Frame: 12 - 36 months after baseline ] [ Designated as safety issue: No ]
  PRET Niger
  
  
• Mortality in 1-5 year old study children [ Time Frame: Over study period ] [ Designated as safety issue: No ]
  PRET Gambia
  
  
• Cause-specific mortality in 1-5 year olds assessed by verbal autopsy [ Time Frame: Over study period ] [ Designated as safety issue: No ]
  PRET Gambia
  
  
• Mortality in adults in the study area [ Time Frame: Over study period ] [ Designated as safety issue: No ]
  PRET Gambia
  
  
• Cause-specific mortality in adults assessed by verbal autopsy [ Time Frame: Over study period ] [ Designated as safety issue: No ]
  PRET Gambia
  
  
• Morbidity among 1-5 year old study children as assessed by height for age, weight for age, weight for height, body mass index and Hackett spleen size [ Time Frame: 30 months after baseline ] [ Designated as safety issue: No ]
  PRET Gambia
  
  
• Serotype distribution, antibiotic sensitivity profile and MLST type of Streptococcus pneumoniae carried in the nasopharynx of study children [ Time Frame: 30 months after baseline ] [ Designated as safety issue: No ]
  PRET Gambia
  
  

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. We will evaluate the efficacy of guiding further mass treatment according to a laboratory test for Chlamydia or WHO guidelines. Where we estimate communities have infection rates less than 5% in sentinel children, or 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.