title: Factors associated with initiation and completion of the quadrivalent human papillomavirus vaccine series in an Ontario cohort of grade 8 girls.
abstract: BACKGROUND
  Although over a hundred million dollars have been invested in offering free quadrivalent human papillomavirus (HPV) vaccination to young girls in Ontario, there continues to be very little information about its usage. In order to successfully guide future HPV vaccine programming, it is important to monitor HPV vaccine use and determine factors associated with use in this population.
  
  
  METHODS
  Linking administrative health and immunization databases, we conducted a population-based, retrospective cohort study of girls eligible for Ontario's Grade 8 HPV vaccination program in Kingston, Frontenac, Lennox, and Addington. We determined the proportion of girls who initiated (at least one dose) and completed (all three doses) the vaccination series overall and according to socio-demographics, vaccination history, health services utilization, medical history, and program year. Multivariable logistic regression was used to estimate the strength of association between individual factors and initiation and completion, adjusted for all other factors.
  
  
  RESULTS
  We identified a cohort of 2519 girls, 56.6% of whom received at least one dose of the HPV vaccine. Among vaccinated girls, 85.3% received all three doses. Vaccination history was the strongest predictor of initiation in that girls who received the measles-mumps-rubella, meningococcal C, and hepatitis B vaccines were considerably more likely to also receive the HPV vaccine (odds ratio 4.89; 95% confidence interval 4.04-5.92). Nevertheless, HPV vaccine uptake was more than 20% lower than that of these other vaccines. In addition, while series initiation was not influenced by income, series completion was. In particular, girls of low income were the least likely to receive all three indicated doses of the HPV vaccine (odds ratio 0.45; 95% confidence interval 0.28-0.72).
  
  
  CONCLUSIONS
  The current low level of HPV vaccine acceptance in Kingston, Frontenac, Lennox, and Addington will likely have important implications in terms of the health benefits and cost-effectiveness of its publicly funded program. We identified important factors associated with series initiation and completion that should be considered in efforts to improve HPV vaccine use in this population.
authors.affiliation: Department of Community Health and Epidemiology, Queen's University, Carruthers Hall, Kingston, ON, K7L 3N6, Canada. leahmariesmith@gmail.com
authors.forename: Leah M
authors.initials: LM
authors.lastname: Smith
authors.forename: Paul
authors.initials: P
authors.lastname: Brassard
authors.forename: Jeffrey C
authors.initials: JC
authors.lastname: Kwong
authors.forename: Shelley L
authors.initials: SL
authors.lastname: Deeks
authors.forename: Anne K
authors.initials: AK
authors.lastname: Ellis
authors.forename: Linda E
authors.initials: LE
authors.lastname: Lévesque
mesh_terms: D000293:Adolescent; D005260:Female; D005380:Financing, Government; D006801:Humans; D017589:Immunization Programs / Q000191:economics / Q000706:statistics & numerical data*; D007182:Income / Q000706:statistics & numerical data; D009864:Ontario; D053918:Papillomavirus Vaccines / Q000008:administration & dosage*; D010342:Patient Acceptance of Health Care / Q000706:statistics & numerical data*; D012189:Retrospective Studies; D014611:Vaccination / Q000706:statistics & numerical data*
chemical_list: D053918:Papillomavirus Vaccines