Objective: To examine the rate and correlates of completion of the quadrivalent human papillomavirus vaccine (HPV4) 3-dose regimen because nonadherence to the regimen may adversely affect vaccine efficacy.
Participants and methods: Female members of Kaiser Permanente Southern California who were 9 to 26 years old, received the first dose of HPV4 between October 2006 and March 2007, and maintained health plan membership 12 months afterward were identified and followed up for regimen completion. We examined the following: (1) demographics/socioeconomic status, (2) primary care physician characteristics, (3) historical health service utilization, (4) women's health-related conditions, and (5) selected immune-related conditions for their association with completion in 2 age groups: 9 to 17 years and 18 to 26 years. Multivariable log-binomial regression was used to directly estimate relative risk (RR).
Results: Of the 34,193 females who initiated HPV4, the completion rate was 41.9% in the 9- to 17-year-old group and 47.1% in the 18- to 26-year-old group. Black race (RR, 0.70; 95% confidence interval [CI], 0.64-0.77) and lower neighborhood education level were associated with lower regimen completion. However, those in the 9- to 17-year-old group who were covered by the state-subsidized program Medi-Cal were more likely to complete the regimen (RR, 1.14; 95% CI, 1.07-1.22). Historical hospitalizations and emergency department visits (RR, 0.92; 95% CI, 0.87-0.96; and RR, 0.96; 95% CI, 0.94-0.98 per visit, respectively) and having a pediatrician were also predictors of noncompletion. A history of sexually transmitted diseases, abnormal Papanicolaou test results, and immune-related conditions (eg, asthma/infections) were not associated with regimen completion.
Conclusion: These findings suggest that factors such as race or socioeconomic status should be considered when human papillomavirus vaccination programs are being designed and evaluated.