Spatial patterns of HPV and Tdap vaccine dose administration and the association of health department clinic access in Georgia counties

Objective: To characterize counties in GA by quantifying administered doses of the HPV and Tdap vaccines collected by the state health department immunization registry and indicators of Health Department (HD) clinic access. Methods: Using a cross sectional study design, secondary data were collected from public health data sources for the years 2016 to 2018 for 159 counties of Georgia. The study population was male and female adolescents aged 13-17. The number of administered HPV and Tdap vaccine doses were modeled in relation to number of private and public HD clinics, number of HD clinics registered in the VFC program and the availability of public transportation using Poisson regression, negative binomial regression, and Bayesian spatial analysis. Results: Choropleth maps showed similar clustering patterns between administered doses of the HPV vaccine and Tdap vaccine and increased counts of administered vaccine doses in counties with both public and private clinics. Administered doses of HPV and Tdap vaccines were found to exhibit spatial dependence across counties. Accounting for spatial dependence, the availability of public transit had a significant positive effect on administered HPV vaccine doses, while the number of private HD clinics had a significant positive effect on administered Tdap vaccine doses. Conclusions: Maps at the county level show vaccination variability, clustering patterns and provide additional insights on the access to health care. Bayesian spatial models are needed to accurately identify and estimate factors associated with administering doses of the HPV and Tdap vaccines. Future work is needed to further examine the utilization of HPV vaccination services among urban groupings.