Gardasil™ HPV Vaccination: Surveillance of Vaccine Usage and Adherence in a Military Population

Objectives: To investigate the usage patterns and adherence rates with the quadrivalent HPV (qHPV) vaccine at Naval Medical Center San Diego.

Methods: This retrospective, cross-sectional study was conducted by using AHLTA (Electronic Health Record of DoD) to identify all qHPV recipients between 2006 and 2009. Charts were reviewed to extract demographic variables and immunization schedules for association analysis. Subjects were assigned intention-to-treat (ITT) if they initiated the series and reached the 1-year anniversary after dose-1 or in-progress (IP) if the series was incomplete and within 1-year. ITT subjects were designated non-adherent or adherent based on 1-2 or 3 doses received.

Results: 6792 females and 46 males with respective mean ages (years) of 19 (95% CI: 10-29) and 27 (95% CI: 9-46) initiated the qHPV series. The evaluable ITT population consisted of 5088 females and 31 males. The adherence rate for females was 32% (1656/5088) versus 3% (1/31) for males. For females, adherence declined from 45%, 24%, to 14% with respect to increasing age: 8-17, 18-26, 27-50years. Adherence declined accordingly by beneficiary status: dependent daughters (43%), spouses (21%) and active duty (16%); and by clinic of vaccine initiation: Pediatrics/Adolescent (45%), Primary Care (38%), Immunization (21%), and OB/GYN (9%). Males were predominantly active duty 84%, vaccinated through immunization clinics 84%, and poorly adherent 3%.

Conclusions: Optimal HPV immunization efficacy is derived from vaccine adherence and HPV naivety. This study of qHPV adherence has provided insight into real-world suboptimal use post-marketing. Usage patterns and adherence rates were significantly associated with demographic characteristics.