title: Non-participation during azithromycin mass treatment for trachoma in The Gambia: heterogeneity and risk factors.
abstract: BACKGROUND
  There is concern that untreated individuals in mass drug administration (MDA) programs for neglected tropical diseases can reduce the impact of elimination efforts by maintaining a source of transmission and re-infection.
  
  
  RESULTS
  Treatment receipt was recorded against the community census during three MDAs with azithromycin for trachoma in The Gambia, a hypo-endemic setting. Predictors of non-participation were investigated in 1-9 year olds using random effects logistic regression of cross-sectional data for each MDA. Two types of non-participators were identified: present during MDA but not treated (PNT) and eligible for treatment but absent during MDA (EBA). PNT and EBA children were compared to treated children separately. Multivariable models were developed using baseline data and validated using year one and two data, with a priori adjustment for previous treatment status. Analyses included approximately 10000 children at baseline and 5000 children subsequently. There was strong evidence of spatial heterogeneity, and persistent non-participation within households and individuals. By year two, non-participation increased significantly to 10.4% overall from 6.2% at baseline, with more, smaller geographical clusters of non-participating households. Multivariable models suggested household level predictors of non-participation (increased time to water and household head non-participation for both PNT and EBA; increased household size for PNT status only; non-inclusion in a previous trachoma examination survey and younger age for EBA only). Enhanced coverage efforts did not decrease non-participation. Few infected children were detected at year three and only one infected child was EBA previously. Infected children were in communities close to untreated endemic areas with higher rates of EBA non-participation during MDA.
  
  
  CONCLUSIONS
  In hypo-endemic settings, with good coverage and no association between non-participation and infection, efforts to improve participation during MDA may not be required. Further research could investigate spatial hotspots of infection and non-participation in other low and medium prevalence settings before allocating resources to increase participation.
authors.affiliation: MRC Tropical Epidemiology Group, London School of Hygiene and Tropical Medicine, London, United Kingdom.
authors.forename: Tansy
authors.initials: T
authors.lastname: Edwards
authors.affiliation: Department of Medical Statistics, London School of Hygiene and Tropical Medicine, London, United Kingdom.
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Allen
authors.affiliation: Department of Clinical Research, London School of Hygiene and Tropical Medicine, London, United Kingdom.
authors.forename: Emma M
authors.initials: EM
authors.lastname: Harding-Esch
authors.affiliation: Department of Clinical Research, London School of Hygiene and Tropical Medicine, London, United Kingdom.
authors.forename: John
authors.initials: J
authors.lastname: Hart
authors.affiliation: Department of Clinical Research, London School of Hygiene and Tropical Medicine, London, United Kingdom; Disease Control and Elimination Theme, Medical Research Council Unit (MRC), Fajara, Banjul, The Gambia.
authors.forename: Sarah E
authors.initials: SE
authors.lastname: Burr
authors.affiliation: Department of Clinical Research, London School of Hygiene and Tropical Medicine, London, United Kingdom; Disease Control and Elimination Theme, Medical Research Council Unit (MRC), Fajara, Banjul, The Gambia.
authors.forename: Martin J
authors.initials: MJ
authors.lastname: Holland
authors.affiliation: National Eye Health Programme, Ministry of Health and Social Welfare, Kanifing, The Gambia.
authors.forename: Ansumana
authors.initials: A
authors.lastname: Sillah
authors.affiliation: Dana Center for Preventive Ophthalmology, Johns Hopkins University, Baltimore, Maryland, United States of America.
authors.forename: Sheila K
authors.initials: SK
authors.lastname: West
authors.affiliation: Department of Clinical Research, London School of Hygiene and Tropical Medicine, London, United Kingdom.
authors.forename: David
authors.initials: D
authors.lastname: Mabey
authors.affiliation: Department of Clinical Research, London School of Hygiene and Tropical Medicine, London, United Kingdom.
authors.forename: Robin
authors.initials: R
authors.lastname: Bailey
mesh_terms: D017963:Azithromycin / Q000008:administration & dosage / Q000627:therapeutic use; D002648:Child; D002675:Child, Preschool; D003140:Communicable Disease Control / Q000379:methods / Q000706:statistics & numerical data; D005260:Female; D005714:Gambia / Q000453:epidemiology; D006801:Humans; D007223:Infant; D008297:Male; D010349:Patient Compliance / Q000706:statistics & numerical data*; D012307:Risk Factors; D014141:Trachoma / Q000188:drug therapy / Q000453:epidemiology / Q000517:prevention & control
chemical_list: D017963:Azithromycin