Effectiveness of interventions to reduce COVID-19 transmission in a large urban jail: a model-based analysis

ObjectivesWe aim to estimate the impact of various mitigation strategies on COVID-19 transmission in a US jail beyond those offered in national guidelines.DesignWe developed a stochastic dynamic transmission model of COVID-19.SettingOne anonymous large urban US jail.ParticipantsSeveral thousand staff and incarcerated individuals.InterventionsThere were four intervention phases during the outbreak: the start of the outbreak, depopulation of the jail, increased proportion of people in single cells and asymptomatic testing. These interventions were implemented incrementally and in concert with one another.Primary and secondary outcome measuresThe basic reproduction ratio, R0, in each phase, as estimated using the next generation method. The fraction of new cases, hospitalisations and deaths averted by these interventions (along with the standard measures of sanitisation, masking and social distancing interventions).ResultsFor the first outbreak phase, the estimated R0 was 8.44 (95% credible interval (CrI): 5.00 to 13.10), and for the subsequent phases, R0,phase 2=3.64 (95% CrI: 2.43 to 5.11), R0,phase 3=1.72 (95% CrI: 1.40 to 2.12) and R0,phase 4=0.58 (95% CrI: 0.43 to 0.75). In total, the jail’s interventions prevented approximately 83% of projected cases, hospitalisations and deaths over 83 days.ConclusionsDepopulation, single celling and asymptomatic testing within jails can be effective strategies to mitigate COVID-19 transmission in addition to standard public health measures. Decision makers should prioritise reductions in the jail population, single celling and testing asymptomatic populations as additional measures to manage COVID-19 within correctional settings.