Caregiver and adolescent factors associated with delayed completion of the three-dose human papillomavirus vaccination series.

Background: Delayed completion of human papillomavirus vaccination (4vHPV) series is common. We sought to identify factors associated with delay.

Methods: This substudy was part of a large prospective, multi-site study recruiting 9-17 year old girls at the time of their third 4vHPV dose to assess immunogenicity associated with prolonged dosing intervals. At participating sites, parents/legal guardians (caregivers) of all enrolled girls (9-17 years old) and enrolled girls aged 14-17 years were approached for participation. Caregivers completed a questionnaire measuring adolescent and caregiver sociodemographic characteristics, caregiver attitudes and beliefs about on-schedule HPV vaccination and HPV vaccine safety, adolescent's health behaviors, barriers to accessing health care, provider office vaccination practices and a Rapid Estimate of Adult Literacy in Medicine (REALM). Participating girls completed a separate questionnaire measuring their attitudes and beliefs about on-schedule HPV vaccination and HPV vaccine safety. Delay was defined as receiving the third 4vHPV dose >12 months after the first. Bivariate, multinomial logistic regression and multivariate logistic regression analyses were used to identify factors predicting delayed completion.

Results: Questionnaires were completed by 482 caregivers and 386 adolescents; 422 caregivers completed a REALM. Delayed 4vHPV dosing occurred in most adolescents (67%). In multivariate analyses, predictors of delayed completion included caregiver demographic factors (self-reported black vs. white race and high school or less education vs. college or more) and an interaction between caregiver's inability to get an immunization appointment as soon as needed and adolescent's type of insurance.

Conclusions: Caregiver's race and educational level, accessibility of immunization appointments, and adolescent's insurance type were found to be related to delays in completion of 4vHPV, but caregiver or adolescent attitudes and beliefs about on-schedule HPV vaccination or HPV vaccine safety were not. Therefore, interventions to improve adherence to recommended vaccination schedules could benefit from a focus on improving access to immunizations. ClinicalTrials.gov (NCT01030562).