Covid-19 in the California State Prison System: An Observational Study of Decarceration, Ongoing Risks, and Risk Factors

BACKGROUND: Correctional institutions nationwide are seeking to mitigate Covid-19-related risks. OBJECTIVE: To quantify changes to California’s prison population since the pandemic began and identify risk factors for Covid-19 infection. DESIGN: We described residents’ demographic characteristics, health status, Covid-19 risk scores, room occupancy, and labor participation. We used Cox proportional hazard models to estimate the association between rates of Covid-19 infection and room occupancy and out-of-room labor, respectively. SETTING: California state prisons (March 1-October 10, 2020). PARTICIPANTS: Residents of California state prisons. MEASUREMENTS: Changes in the incarcerated population’s size, composition, housing, and activities. For the risk factor analysis, the exposure variables were room type (cells vs dormitories) and labor participation (any room occupant participating in the prior 2 weeks) and the outcome variable was incident Covid-19 case rates. RESULTS: The incarcerated population decreased 19.1% (119,401 to 96,623) during the study period. On October 10, 2020, 11.5% of residents were aged ≤60, 18.3% had high Covid-19 risk scores, 31.0% participated in out-of-room labor, and 14.8% lived in rooms with ≤10 occupants. Nearly 40% of residents with high Covid-19 risk scores lived in dormitories. In 9 prisons with major outbreaks (6,928 rooms; 21,750 residents), dormitory residents had higher infection rates than cell residents (adjusted hazard ratio [AHR], 2.51 95%CI, 2.25-2.80) and residents of rooms with labor participation had higher rates than residents of other rooms (AHR, 1.56; 95%CI, 1.39-1.74). LIMITATIONS: Inability to measure density of residents’ living conditions or contact networks among residents and staff. CONCLUSION: Despite reductions in room occupancy and mixing, California prisons still house many medically vulnerable residents in risky settings. Reducing risks further requires a combination of strategies, including rehousing, decarceration, and vaccination. FUNDING SOURCES: Horowitz Family Foundation; National Institute on Drug Abuse; National Science Foundation Graduate Research Fellowship; Open Society Foundations.