HPV vaccination among adolescents lags behind those of other adolescent vaccines, including the tetanus-diphtheria-acellular pertussis (Tdap) and the meningococcal conjugate vaccine (MCV4). This research sought to understand barriers to HPV vaccine uptake among adolescents in Colorado, with focus on providers serving low-income populations who are at high risk for HPV related cancer and other diseases.

Colorado's Vaccine for Children (VFC) and primary care service area data were used to identify high and low HPV vaccine ordering practices compared to Tdap vaccine and compared to neighboring practices. Using adapted grounded theory, semi-structured interviews were conducted with 26 providers from these practices. Hypotheses from qualitative findings were tested using All Payer Claims Database data. Logit regression was used to model likelihood of HPV vaccine initiation and completion among children ages 11-18. Oaxaca-Blinder (OB) regression decomposition was used to identify explained and unexplained factors between ethnicity and public- versus privately-insured groups.

Qualitative research results described parental, provider, and policy level barriers and facilitators to HPV vaccine delivery. Barriers included parental vaccine hesitancy and lack of consistent recommendation by providers. Steps taken to improve HPV vaccine acceptability included creative communications with parents and adolescents about HPV and extended office hours to administer vaccines.

Quantitative analysis showed that males, adolescents with male providers, and patients who saw non-primary care providers were significantly less likely to initiate and complete the HPV vaccine series. Hispanics were 12.15 percentage point more likely to initiate and 2.99 percentage points more likely to complete the HPV vaccine series compared to non-Hispanics. Additionally, publicly insured adolescents were 3.99 more likely to initiate HPV vaccine compared to non-publicly insured, however, non-publicly insured were 5.4 percentage points more likely to complete the three dose HPV vaccine series compared to publicly insured adolescents. OB decomposition showed explained and unexplained factors that drove the observed disparity in HPV vaccine rate.

Even though higher vaccination rates among low income groups than non-low income groups are observed, significant challenges to HPV vaccine initiation and completion remain. However, understanding the specific factors that influence and explain HPV vaccine uptake is crucial for implementing interventions to improve HPV vaccination.