Outbreaks of COVID-19 variants in US prisons: a mathematical modelling analysis of vaccination and reopening policies

Abstract

Background Residents of prisons have experienced disproportionate COVID-19-related health harms. To control outbreaks, many prisons in the USA restricted in-person activities, which are now resuming even as viral variants proliferate. This study aims to use mathematical modelling to assess the risks and harms of COVID-19 outbreaks in prisons under a range of policies, including resumption of activities.Methods We obtained daily resident-level data for all California state prisons from Jan 1, 2020, to May 15, 2021, describing prison layouts, housing status, sociodemographic and health characteristics, participation in activities, and COVID-19 testing, infection, and vaccination status. We developed a transmission-dynamic stochastic microsimulation parameterised by the California data and published literature. After an initial infection is introduced to a prison, the model evaluates the effect of various policy scenarios on infections and hospitalisations over 200 days. Scenarios vary by vaccine coverage, baseline immunity (0%, 25%, or 50%), resumption of activities, and use of non-pharmaceutical interventions (NPIs) that reduce transmission by 75%. We simulated five prison types that differ by residential layout and demographics, and estimated outcomes with and without repeated infection introductions over the 200 days.Findings If a viral variant is introduced into a prison that has resumed pre-2020 contact levels, has moderate vaccine coverage (ranging from 36% to 76% among residents, dependent on age, with 40% coverage for staff), and has no baseline immunity, 23-74% of residents are expected to be infected over 200 days. High vaccination coverage (90%) coupled with NPIs reduces cumulative infections to 2-54%. Even in prisons with low room occupancies (ie, no more than two occupants) and low levels of cumulative infections (ie, <10%), hospitalisation risks are substantial when these prisons house medically vulnerable populations. Risks of large outbreaks (>20% of residents infected) are substantially higher if infections are repeatedly introduced.Interpretation Balancing benefits of resuming activities against risks of outbreaks presents challenging trade-offs. After achieving high vaccine coverage, prisons with mostly one-to-two-person cells that have higher baseline immunity from previous outbreaks can resume in-person activities with low risk of a widespread new outbreak, provided they maintain widespread NPIs, continue testing, and take measures to protect the medically vulnerable.

Factors associated with COVID-19 vaccine acceptance and hesitancy among residents of Northern California jails

“…High vaccine coverage is needed to mitigate COVID-19 transmission in congregate, high-density settings such as prisons and jails, especially amidst viral variants ( Ryckman et al, 2021 , Chin et al, 2021 ). Studies in US prisons have identified differences in COVID-19 vaccine uptake across demographic groups ( Chin et al, 2021 , Hagan et al, 2021 ).…”

Factors associated with COVID-19 vaccine acceptance and hesitancy among residents of Northern California jails

“…High vaccine coverage is needed to mitigate COVID-19 transmission in congregate, high-density settings such as prisons and jails, especially in the context of existing and future viral variants [9,10]. Despite the importance of achieving high vaccination rates in this population, there is a paucity of data on COVID-19 vaccine acceptance and reasons for hesitancy among incarcerated individuals to guide evidence-based vaccination efforts.…”

A large outbreak of COVID-19 in a UK prison, October 2020 to April 2021

“…Modelling has shown that vaccinating everyone living and working in prisons is the most effective strategy for reducing COVID-19 cases, transmission and outbreaks, with an 89% reduction in cases over three years [2]. Combination of high vaccine coverage with other non-pharmaceutical interventions has been shown to reduce cumulative infections by up to 54% in another model [19].…”