County-level correlates of completed HPV vaccination in Indiana

The Healthy People 2030 goal is for 80% of all adolescents to complete their HPV vaccination series. Per the 2021, National Immunization Survey-Teen (NIS-Teen), 61.7% of adolescents have completed the series, and Indiana lags below the national average (55.2%). The present study estimated the 2-dose HPV vaccine series completion rates across Indiana counties among individuals aged 9-14 years who received their first dose of vaccine and determined what factors were associated with series completion at the county level. The association of county-level sociodemographic and health measures with series completion was also examined. Data were extracted from the Indiana Immunization Information System (IIS), administered by the Indiana Department of Health. All vaccine providers are required to report all immunizations to the system for any patient under age 19 years. All Indiana children ages 9-14 years at the time of first dose who had initiated HPV vaccination in 2017 or 2018 were included. Two-dose series completion was evaluated through October of 2020, allowing a minimum gap of 22 months from first dose administration. All statistical analyses were conducted at the county-level. The Indiana HPV vaccination series completion rate among individuals that received the first dose was on average 73% across counties, ranging from 55.7% to 90.4%. Higher series completion was positively associated with primary care providers per capita, participation in mammography screening among Medicare enrollees, median household income, life expectancy, percentage of residents with some college, percentage of adults up-to-date with colonoscopy screening, and percentage of adults with flu vaccine. There was wide variability in series completion across Indiana counties. HPV series completion was associated with county-level sociodemographic and health measures, particularly variables reflecting difficulties with access to care and lack of financial resources.