title: Exploring the heterogeneity among partially vaccinated children in a population-based cohort.
abstract: BACKGROUND
  Vaccination status is often categorized as complete or not-complete. This ignores the potentially important heterogeneity in children whose vaccinations are not-complete. We sought to subcategorize not-completely vaccinated children and determine whether characteristics differed among these subgroups.
  
  
  METHODS
  This retrospective cohort study assessed vaccination status at 2 years of age for 43,965 children in the 2008 Alberta (Canada) birth cohort who were registered with provincial vital statistics records. Children were categorized (based on the five routinely scheduled childhood vaccines) as complete, incomplete, selective, or non-vaccination status. Characteristics derived from administrative health databases were used to determine factors associated with vaccination status.
  
  
  RESULTS
  Population-level vaccination status at 2 years of age was found to be: 71.1% complete and 28.9% not complete (21.9% incomplete, 2.0% selective, and 5.1% non-vaccinated). Midwife delivery at home, compared to physician delivery in hospital, was strongly associated with non-vaccination status (adjusted odds ratio [aOR] 51.70, 95% CI 37.10-72.10). Factors that might pose barriers to vaccination, such as single marital status (aOR 1.58, 95% CI 1.49-1.67), large number of household children (≥4 vs. 1) (aOR 3.24, 95% CI 2.95-3.54), and multiple household moves (≥3 vs. 0) (aOR 1.69, 95% CI 1.35-2.10), were all strongly associated with incomplete vaccination status.
  
  
  CONCLUSIONS
  Of the children who were not completely vaccinated at age 2, the vast majority had started but not completed the vaccination series, while a smaller number were selectively vaccinated or not vaccinated at all. Distinct differences are present among these groups that require attention when addressing vaccine coverage.
authors.affiliation: Alberta Health Surveillance and Assessment, Edmonton, Alberta, Canada; School of Public Health, University of Alberta, Edmonton, Alberta, Canada. Electronic address: chris.bell@gov.ab.ca.
authors.forename: Christopher A
authors.initials: CA
authors.lastname: Bell
authors.affiliation: Alberta Health Surveillance and Assessment, Edmonton, Alberta, Canada; Department of Community Health Sciences, University of Calgary, Calgary, Alberta, Canada.
authors.forename: Kimberley A
authors.initials: KA
authors.lastname: Simmonds
authors.affiliation: Department of Pediatrics, University of Calgary, Calgary, Alberta, Canada; Faculty of Nursing, University of Alberta, Edmonton, Alberta, Canada.
authors.forename: Shannon E
authors.initials: SE
authors.lastname: MacDonald
mesh_terms: D000416:Alberta; D004363:Drug Utilization; D005260:Female; D006801:Humans; D007223:Infant; D008297:Male; D012189:Retrospective Studies; D012923:Social Class; D014611:Vaccination / Q000706:statistics & numerical data*; D014612:Vaccines / Q000008:administration & dosage*
chemical_list: D014612:Vaccines
keywords: Immunization; Incomplete; Partial; Selective status; Vaccination; Vaccine