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

Objectives We aim to estimate the impact of various mitigation strategies on COVID-19 transmission in a US jail beyond those offered in national guidelines. Design We developed a stochastic dynamic transmission model of COVID-19. Setting One anonymous large urban US jail. Participants Several thousand staff and incarcerated individuals. Interventions There 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 measures The 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). Results For 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. Conclusions Depopulation, 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.