Spatial Analysis of Social Vulnerability and Firearm Injury EMS Encounters in King County, Washington, 2019-2023

Objectives: In the United States, firearm injuries disproportionately occur in low-income communities and among racial and ethnic minority populations. Recognizing these patterns across social conditions is vital for effective public health interventions. Using timely and localized data, we examined the association between social vulnerability and firearm injuries in King County, Washington. Methods: For this ecological, cross-sectional study, we used health reporting areas (HRAs) (n = 61), a subcounty geography of King County. We obtained HRA-level counts of firearm injuries by using responses from King County emergency medical services (EMS) from 2019 through 2023. We measured HRA-level social vulnerability by using the Social Vulnerability Index (SVI) from the Centers for Disease Control and Prevention/Agency for Toxic Substances and Disease Registry, categorized into tertiles (low, moderate, and high SVI). We used bivariate choropleth mapping to illustrate spatial associations between SVI and rates of firearm injuries per 10 000 residents. We used Bayesian spatial negative binomial regression to quantify the strength of these associations. Results: Bivariate choropleth mapping showed a correlation between SVI and rates of firearm injuries. In spatial models, HRAs categorized as high SVI had a 3 times higher rate of firearm injuries than HRAs categorized as low SVI (incidence rate ratio = 3.01; 95% credible interval, 2.02-4.47). Rates of firearm injuries were also higher in HRAs categorized as moderate versus low SVI (incidence rate ratio = 1.72; 95% credible interval, 1.23-2.40). Conclusion: In King County, areas with high social vulnerability had high rates of EMS responses to firearm injuries. SVI can help identify geographic areas for intervention and provide a framework for identifying upstream factors that might contribute to spatial disparities in firearm injuries.