Predicting mobile health clinic utilization for COVID-19 vaccination in South Carolina: A statistical framework for strategic resource allocation.

Mobile health clinics (MHCs) are effective tools for providing health services to disadvantaged populations, especially during health emergencies. However, patient utilization of MHC services varies substantially. Strategies to increase utilization are needed to maximize the effectiveness of MHC services by serving more patients in need. The purpose of this study is to develop a statistical framework to identify and prioritize high-risk communities for delivery of MHCs during health emergencies. Prisma Health MHCs delivered COVID-19 vaccines to communities throughout South Carolina between February 20, 2021, and February 17, 2022. In this retrospective study, we used generalized linear mixed effects models and ordinal logistic regression models to identify factors associated with, and predictive of, MHC utilization for COVID-19 vaccination by census tract. The MHCs conducted 260 visits to 149 sites and 107 census tracts. The site-level analysis showed that visits to schools (RR = 2.17, 95% CI = 1.47-3.21), weekend visits (RR = 1.38, 95% CI = 1.03-1.83), and visits when the resources were limited (term 1: 7.11, 95% CI = 4.43-11.43) and (term 2: 2.40, 95% CI = 1.76-3.26) were associated with greater MHC utilization for COVID-19 vaccination. MHC placement near existing vaccination centers (RR = 0.79, 95% CI = 0.68-0.93) and hospitals (RR = 0.83, 95% CI = 0.71-0.96) decreased utilization. Predictive models identified 1,227 (94.7%) census tracts with more than 250 individuals per MHC visit when vaccine resources were limited. Predictions showed satisfactory accuracy (72.6%). The census tracts with potential of high MHC demand had higher adolescent, 30-44 years old, and non-White populations; lower Primary Care Practitioners per 1,000 residents; fewer hospitals; and higher cumulative COVID-19 emergency department visits and deaths (compared to census tracts with low MHC demand). After the vaccines became widely available, the demand at MHCs declined. These study findings can improve MHC allocation by identifying and prioritizing medically underserved communities for strategic delivery of these limited resources, especially during health emergencies.