Leibowitz AI, Siedner MJ, Tsai AC, et al. - The results demonstrated that within 14 Massachusetts state prisons, increased crowding was correlated with elevated incidence rates of COVID-19 in this longitudinal ecological study. Strategies should be explored by researchers and policymakers that reduce prison crowding, such as decarceration, as potential ways to mitigate COVID-19 morbidity and mortality among incarcerated persons.

• During the study period, there were on average 6,876 people incarcerated in 14 prisons.

• During the observation period, the median level of crowding ranged from 25% to 155% of design capacity.

• They observed higher COVID-19 incidence in prisons where the incarcerated population was a larger percentage of the prison’s design capacity (incidence rate ratio [IRR] per 10-percentage-point difference, 1.14; 95% CI, 1.03-1.27).

• They further observed lower COVID-19 incidence in prisons where a higher proportion of incarcerated people were housed in single-cell units (IRR for each 10-percentage-point increase in single-cell units, 0.82; 95% CI, 0.73-0.93).

• It was shown that COVID-19 transmission in the surrounding county was consistently correlated with COVID-19 incidence in prisons (IRR [for each increase of 10 cases per 100,000 person-weeks in the community], 1.06; 95% CI, 1.05-1.08).