Health and Economic Impact of COVID-19 Surveillance Testing in Seattle Homeless Shelters: A Cost-Effectiveness Analysis.

Introduction: COVID-19 surveillance in congregate settings is important to mitigating disease, but the health and economic impact of testing remains unclear. Methods: The authors developed a Markov model to project the cost-utility of COVID-19 testing strategies in homeless shelters from the healthcare payer and societal perspective over 1 year. Model inputs utilized data from residents aged ≥18 years across 23 Seattle shelters from January 1, 2020, to May 31, 2021. No in-shelter surveillance was compared with scenarios of 2 COVID-19 testing strategies implemented monthly: polymerase chain reaction (PCR) testing and rapid antigen testing; scenarios in which only PCR testing was available were also evaluated. The primary health outcome was quality-adjusted life years. Interventions were considered cost-effective if the incremental cost-effectiveness ratio was ≤$150,000 per quality-adjusted life year and dominant if they saved costs and provided health effects. Results: When assuming the availability of both antigen and PCR tests, most rapid antigen testing strategies were cost-effective, whereas PCR testing was dominated by antigen testing. Compared with no in-shelter surveillance, antigen testing increased mean quality-adjusted life years by 0.0009 (0.03% infections averted) at an incremental cost of $97/resident from the healthcare perspective (incremental cost-effectiveness ratio=$112,352/quality-adjusted life year gained) and $8/resident from the societal perspective (incremental cost-effectiveness ratio=$9,627/quality-adjusted life year gained) at 75% vaccination coverage. PCR testing was not cost-effective when antigen testing was available but was cost-effective compared with no surveillance at low vaccination coverage levels (<30% coverage from the healthcare perspective and ≤48% coverage from the societal perspective). Probabilistic sensitivity analysis showed that antigen testing was cost-effective in 62% and 86% of simulations from the healthcare and societal perspectives, respectively. Conclusions: Modeled findings show that COVID-19 testing in shelters can be a cost-effective pandemic response. Antigen testing remained cost-effective at high vaccination levels, whereas PCR testing was most effective at low vaccination levels if antigen testing was not available.