Evidence of effective delivery of the human papillomavirus (HPV) vaccine through a publicly funded, school-based program: the Ontario Grade 8 HPV Vaccine Cohort Study

Abstract

Background: Proper administration of the human papillomavirus (HPV) vaccine (three doses at 0, 2, and 6 months) will likely influence the vaccine's effectiveness and the impact of vaccination programs on health outcomes. Therefore, we assessed HPV vaccine series completion and on-time dosing in Canada's largest publicly funded, school-based HPV vaccination program.

Methods: Using administrative health and immunization databases, we identified a population-based cohort of girls eligible for Ontario's Grade 8 HPV vaccination program in the 2007/08-2009/10 program years who received at least one dose of the vaccine. We determined the number of doses received and calculated the percentage of girls that completed the three-dose series in Grade 8 and Grades 8-9. To assess on-time dosing, the number of days between doses 1-2, 2-3, and 1-3 was calculated and categorized (e.g., too short, on schedule, too long) based on the manufacturer's recommendations. Analyses were also stratified by program year.

Results: We identified a cohort of 55,798 girls who initiated the vaccination series. Series completion was high in the Grade 8 window (81.8%) and increased by approximately 6% in Grade 9. Series completion was similar across the three program years. 70.8%, 98.5%, and 86.1% of girls were classified as 'on schedule' for dosing intervals 1-2, 2-3, and 1-3, respectively; 70.0% of girls received all three doses in perfect accordance with dosing recommendations. Stratification revealed that on-time dosing was highest in the first two years of the program (85.6% and 80.6%), but dropped to 42.1% in the 2009/10 year when H1N1 vaccination programs were prioritized.

Conclusions: Our study demonstrates that delivery of the HPV vaccine through a free, school-based program is an effective method of ensuring high completion and on-time dosing, but may not be sufficient to guarantee high coverage.

Figure 1

Geographic representation of participating health units. The green regions represent health units whose immunization records were available at the time of the analysis

Figure 2

Number of doses received during the program eligibility period, stratified by program year. *Proportion significantly different from previous program year (p<0.05).

Figure 3

Completion of the three-dose series across program year, according to eligibility period. *Proportion in program eligibility period (i.e., Grade 8-9) significantly different from proportion in Grade 8 eligibility period (p<0.0001).

Figure 4

Compliance with recommended dosing intervals.