Determinants of non-uptake of the quadrivalent HPV vaccine; The Ontario Grade 8 HPV Vaccine Cohort Study
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Background: In 2007, the Canadian federal budget provided $300 million over three years to the provinces and territories to implement publicly-funded HPV immunization programs. Current estimates indicate that HPV vaccine uptake varies significantly across Canada and is reported to be lowest in Ontario at 53%. There is a paucity of literature on the determinants of HPV vaccine uptake in the Canadian context, therefore further research is needed. Objectives: To describe the patterns of HPV vaccine non-uptake across health units in Ontario, and identify the individual- and health unit (ecologic)-level factors that influenced HPV immunization decision-making between 2007 and 2011. Methods: The study linked administrative health and immunization databases to identify a retrospective population-based cohort of 144,047 girls eligible for Ontario's school-based HPV immunization program between 2007 and 2011. In this study a girl was considered vaccinated if she received at least 1 dose, otherwise she was considered unvaccinated. Ecologic or health unit-level factors that may have influenced HPV vaccine decision-making were assessed, as well as individual-level predictors including clinical characteristics and sociodemographics. A population-average model based on generalized estimating equations was used to identify determinants associated with non-uptake. Results: In all, 49.3% of girls from 21 public health units refused HPV immunization between 2007 and 2011. Non-uptake varied across health units, from 41.82% to 60.30%. In multivariate analyses, non-uptake was strongly associated with a history of autism (OR=1.60; 95% CI 1.34, 1.90) and Down's syndrome (OR=1.37; 95% CI 1.16, 1.63), refusal of mandatory and optional vaccines (OR=2.23; 95% CI 2.07, 2.4, and OR=3.96; 95% CI 3.87, 4.05, respectively), and infrequent physician visits (OR=1.45; 95% CI 1.35, 1.55). Contextual or health unit-level characteristics appeared to have a weak influence on vaccine decision-making. Conclusions: HPV immunization could lead to a lower risk of developing and dying from HPV-related cancers; however, non-uptake of this vaccine is high. Concerted efforts are needed to reduce missed opportunities during medical consultations, to refine communication strategies and activities to address the information needs of special groups, as well as to develop cross-sectoral collaborations to support the delivery of publicly-funded HPV immunization to schools across Canada.