Importance: The quadrivalent human papillomavirus (HPV) vaccine was licensed for use in 9- through 26-year-old females in 2006. Postlicensure studies in Australia, Denmark, and Canada have demonstrated vaccine effectiveness against abnormal cervical cytology results. However, there are limited data describing postlicensure effectiveness in the United States, particularly among minority females at higher risk for HPV infection and cervical cancer.
Objective: To examine the effect of HPV vaccination on abnormal cervical cytology results among minority females.
Design, setting, and participants: Retrospective cohort study conducted between January 2007 and January 2014 at 16 academically affiliated community clinics serving a low-income minority population. Included in this study was a population-based sample of 16 266 females aged 11 through 20 years as of January 1, 2007, who received care at a participating clinic on or after that date.
Exposure: Human papillomavirus vaccination, stratified by the number of doses.
Main outcomes and measures: Cervical cytology abnormality following either HPV vaccination or, if unvaccinated, the first missed opportunity for HPV vaccination after January 1, 2007. Abnormalities were defined as atypical glandular cells, atypical squamous cells of undetermined significance, atypical squamous cells, cannot exclude a high-grade squamous intraepithelial lesion, low-grade squamous intraepithelial lesions, or high-grade squamous intraepithelial lesions.
Results: There were 4127 female patients who initiated quadrivalent HPV vaccination or had their first missed HPV vaccination opportunity from 11 through 20 years of age and underwent subsequent cervical cytology screening. The patients were primarily Spanish speaking (n = 2297; 58.3%) and publicly insured (n = 3801; 92.1%). The detection rate for an abnormal cervical cytology result during the observation period was lower among vaccinated (≥1 dose) (79.1 per 1000 person-years) vs unvaccinated (125.7 per 1000 person-years) females. The risk for an abnormal cervical cytology result was lower among vaccinated vs unvaccinated females (hazard ratio [HR], 0.64; 95% CI, 0.57-0.73), particularly if the 3-dose series was completed (HR, 0.48; 95% CI, 0.41-0.56) or if the vaccine was administered from 11 through 14 years of age (≥1 dose: HR, 0.36; 95% CI, 0.16-0.79; 3 doses: HR, 0.27; 95% CI, 0.12-0.63). This protective effect remained after adjusting for demographics, clinic type, abnormal baseline cervical cytology result, and baseline Chlamydia screening (as proxy for sexual experience).
Conclusions and relevance: This study demonstrated the HPV vaccine is effective in a real-world setting of high-risk patients with variable HPV vaccination patterns.