Spatiotemporal transmission and control of a COVID-19 outbreak in a high-rise detention center, South Korea: a retrospective outbreak investigation

Correctional facilities are highly vulnerable to respiratory virus outbreaks due to crowding, shared spaces, limited isolation capacity, and frequent population movement. Evidence from high-rise detention settings remains limited. We conducted a retrospective outbreak investigation and epidemiologic analysis of a COVID-19 outbreak in a high-rise detention center in Seoul, South Korea, from January to March 2022. Demographic, clinical, and vaccination data were obtained from interviews, detention records, and national registries. Attack rates were estimated at the floor and building levels. Exploratory vaccine effectiveness (VE) was estimated using a modified Poisson regression, adjusting for sex, age, prior infection, and proximity to confirmed cases. A total of 492 cases were identified (474 inmates, 18 staff), predominantly Omicron. The cumulative inmate attack rate was 24.0% (474/1,977). Early transmission was rapid and spatially clustered, with the highest ward-level attack rate on the 7th floor of Building 4, increasing from 54.7% (29/53) initially to 88.7% (47/53) by the end of the outbreak. Compared with no vaccination, receipt of a booster dose was associated with an adjusted VE against infection of 23.5% (95% CI 3.8%–39.1%). Layered interventions, including modified lockdowns, contact tracing, mass and targeted testing, and de-densification, helped bring the outbreak under control within approximately one month. Five inmates required hospitalization, and no deaths were reported. In high-rise detention facilities, crowding and shared environments can accelerate the spread of SARS-CoV-2. Early, intensive, multi-layered interventions—combined with booster vaccination—can substantially reduce within-facility transmission and severe outcomes.