title: Clustered lot quality assurance sampling: a pragmatic tool for timely assessment of vaccination coverage.
abstract: OBJECTIVE
  To evaluate oral poliovirus vaccine (OPV) coverage of the November 2009 round in five Northern Nigeria states with ongoing wild poliovirus transmission using clustered lot quality assurance sampling (CLQAS).
  
  
  METHODS
  We selected four local government areas in each pre-selected state and sampled six clusters of 10 children in each Local Government Area, defined as the lot area. We used three decision thresholds to classify OPV coverage: 75-90%, 55-70% and 35-50%. A full lot was completed, but we also assessed in retrospect the potential time-saving benefits of stopping sampling when a lot had been classified.
  
  
  RESULTS
  We accepted two local government areas (LGAs) with vaccination coverage above 75%. Of the remaining 18 rejected LGAs, 11 also failed to reach 70% coverage, of which four also failed to reach 50%. The average time taken to complete a lot was 10 h. By stopping sampling when a decision was reached, we could have classified lots in 5.3, 7.7 and 7.3 h on average at the 90%, 70% and 50% coverage targets, respectively.
  
  
  CONCLUSIONS
  Clustered lot quality assurance sampling was feasible and useful to estimate OPV coverage in Northern Nigeria. The multi-threshold approach provided useful information on the variation of IPD vaccination coverage. CLQAS is a very timely tool, allowing corrective actions to be directly taken in insufficiently covered areas.
authors.affiliation: Epidemiology and Surveillance Unit, National Institute of Public Health and the Environment, Bilthoven, The Netherlands.
authors.forename: K
authors.initials: K
authors.lastname: Greenland
authors.forename: M
authors.initials: M
authors.lastname: Rondy
authors.forename: A
authors.initials: A
authors.lastname: Chevez
authors.forename: N
authors.initials: N
authors.lastname: Sadozai
authors.forename: A
authors.initials: A
authors.lastname: Gasasira
authors.forename: E A
authors.initials: EA
authors.lastname: Abanida
authors.forename: M A
authors.initials: MA
authors.lastname: Pate
authors.forename: O
authors.initials: O
authors.lastname: Ronveaux
authors.forename: H
authors.initials: H
authors.lastname: Okayasu
authors.forename: B
authors.initials: B
authors.lastname: Pedalino
authors.forename: L
authors.initials: L
authors.lastname: Pezzoli
mesh_terms: D002675:Child, Preschool; D016000:Cluster Analysis; D005260:Female; D006801:Humans; D017589:Immunization Programs; D007223:Infant; D055810:Lot Quality Assurance Sampling / Q000379:methods; D008297:Male; D009549:Nigeria; D011055:Poliovirus Vaccine, Oral / Q000008:administration & dosage*; D011785:Quality Assurance, Health Care; D014611:Vaccination / Q000592:standards / Q000706:statistics & numerical data*
chemical_list: D011055:Poliovirus Vaccine, Oral