COVID-19 rapid testing in a homeless shelter: Lessons for equitable access and sustainable pandemic response.

People experiencing homelessness (PEH) faced heightened vulnerability during the COVID-19 pandemic, yet little is known about how frontline homelessness service organizations navigated the public health responsibilities that shifted onto them as broader systems strained. This study provides a longitudinal qualitative analysis of on-site rapid COVID-19 testing implemented at a large Midwestern homeless shelter, examining how multi-level structural conditions shaped the feasibility, ethics, and sustainability of testing over the course of the pandemic. Using semi-structured interviews with shelter guests (n = 42) and staff (n = 12) alongside document and policy timeline analyses (March 2020-January 2023), we conducted reflexive thematic analysis guided by a socioecological framework. Findings show that on-site rapid testing reduced longstanding barriers to care for PEH, offered reassurance in a high-risk environment, and enabled timely outbreak control. However, limited isolation capacity, rapidly evolving guidance, and the withdrawal of external resources generated significant operational and ethical challenges. As federal, state, and local supports diminished, responsibility for disease mitigation increasingly shifted onto the shelter, revealing the institutional precarity of social service agencies that were pushed into assuming public health responsibilities despite lacking the infrastructure to sustain them. Ultimately, shelter leadership discontinued on-site rapid testing after determining that continued isolation and outbreak management were incompatible with the organization's mission and physical constraints. This study demonstrates that while rapid testing can advance health equity for structurally vulnerable populations, sustainability requires coordinated policy frameworks, dedicated resources, and recognition of the limits of frontline service organizations. These findings have implications for designing effective and equitable public health responses beyond COVID-19.