From the report:
Because policymakers failed to take steps to prevent the spread of the virus in prisons and jails, correctional facilities have topped The New York Times’ list of largest outbreaks for months. Not only did officials do little to prevent the spread of COVID-19 within correctional facilities, but they also did little to prevent the transmission of the virus from prison and jail hotspots to nearby surrounding communities. As a consequence, and as our analyses show, ignoring, downplaying, and distorting this systematic failure left communities exposed.
These findings underscore the connection between mass incarceration and public health: At both the local (county) and broader community (areas that share a local economy) levels, larger incarcerated populations were associated with earlier reported cases of COVID-19 in the spring of 2020 and with a spike in confirmed cases over the summer of 2020.