Prison Crowding and COVID-19 Incidence Rates in Massachusetts Prisons | Public Health | JN Learning | AMA Ed Hub [Skip to Content]
[Skip to Content Landing]

Association Between Prison Crowding and COVID-19 Incidence Rates in Massachusetts Prisons, April 2020-January 2021

Educational Objective
To identify the key insights or developments described in this article
1 Credit CME
Key Points

Question  Is prison crowding associated with the risk of COVID-19 among incarcerated persons?

Findings  In this longitudinal ecological study including all incarcerated persons in 14 Massachusetts state prisons from April 2020 to January 2021, on average 6876 persons, COVID-19 incidence was significantly higher in prisons operating at a higher percentage of their design capacity and was significantly lower in prisons where a higher proportion of incarcerated people were housed in single-cell units.

Meaning  Prison crowding was associated with increased COVID-19 incidence rates; strategies that reduce crowding and increase single-cell occupancy should be explored to mitigate COVID-19 risk in prisons.


Importance  COVID-19 incidence and mortality are higher among incarcerated persons than in the general US population, but the extent to which prison crowding contributes to their COVID-19 risk is unknown.

Objective  To estimate the associations between prison crowding, community COVID-19 transmission, and prison incidence rates of COVID-19.

Design, Setting, and Participants  This was a longitudinal ecological study among all incarcerated persons in 14 Massachusetts state prisons between April 21, 2020, and January 11, 2021.

Exposures  The primary exposure of interest was prison crowding, measured by (1) the size of the incarcerated population as a percentage of the prison’s design capacity and (2) the percentage of incarcerated persons housed in single-cell units. The analysis included the weekly COVID-19 incidence in the county where each prison is located as a covariate.

Main Outcomes and Measures  The primary outcome was the weekly COVID-19 incidence rate as determined by positive SARS-CoV-2 tests among incarcerated persons at each prison over discrete 1-week increments.

Results  There was on average 6876 people incarcerated in 14 prisons during the study period. The median level of crowding during the observation period ranged from 25% to 155% of design capacity. COVID-19 incidence was significantly higher 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). COVID-19 incidence was lower 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). COVID-19 transmission in the surrounding county was consistently associated 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).

Conclusions and Relevance  This longitudinal ecological study found that within 14 Massachusetts state prisons, increased crowding was associated with increased incidence rates of COVID-19. Researchers and policy makers should explore strategies that reduce prison crowding, such as decarceration, as potential ways to mitigate COVID-19 morbidity and mortality among incarcerated persons.

Sign in to take quiz and track your certificates

Buy This Activity

JN Learning™ is the home for CME and MOC from the JAMA Network. Search by specialty or US state and earn AMA PRA Category 1 CME Credit™ from articles, audio, Clinical Challenges and more. Learn more about CME/MOC

Article Information

Accepted for Publication: May 28, 2021.

Published Online: August 9, 2021. doi:10.1001/jamainternmed.2021.4392

Corresponding Author: Amir M. Mohareb, MD, Medical Practice Evaluation Center, Massachusetts General Hospital, 100 Cambridge St, 16th Floor, Boston, MA 02114 (

Author Contributions: Ms Leibowitz and Dr Mohareb had full access to all of the data in the study and take responsibility for the integrity of the data and the accuracy of the data analysis.

Concept and design: All authors.

Acquisition, analysis, or interpretation of data: All authors.

Drafting of the manuscript: Leibowitz, Mohareb.

Critical revision of the manuscript for important intellectual content: All authors.

Statistical analysis: All authors.

Administrative, technical, or material support: Mohareb.

Supervision: Tsai, Mohareb.

Conflict of Interest Disclosures: Ms Leibowitz reported provision of pro bono advising in support of Prisoners’ Legal Services of Massachusetts in litigation against the Massachusetts Department of Correction regarding the agency’s response to COVID-19. Dr Tsai reported receiving grants from the Sullivan Family Foundation during the conduct of the study; other from Public Library of Science (stipend for work as specialty consulting editor for PLOS Medicine) and other from Elsevier (stipend for work as editor in chief of SSM-Mental Health) outside the submitted work. Dr Mohareb reported receiving grants from the National Institutes of Health (T32AI007433) outside the submitted work; and provision of pro bono advising and written expert declarations in the following litigation regarding COVID-19 and incarcerated persons: Mays v Dart (Ill 2020), Foster v Mici (Mass 2020, 2021), and Savino v Hodgson (Mass 2020). No other disclosures were reported.

Funding/Support: This work was supported by the National Institutes of Health (grant No. T32 AI007433 to Dr Mohareb). Dr Tsai acknowledges funding support from the Sullivan Family Foundation.

Role of the Funder/Sponsor: The funders had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; preparation, review, or approval of the manuscript; and decision to submit the manuscript for publication.

Disclaimer: The contents of this article are solely the responsibility of the authors and do not necessarily represent the official views of the National Institutes of Health or of the Sullivan Family Foundation.

Walmsley  R . World prison population list (12th edition). Accessed July 8, 2021.
Saloner  B , Parish  K , Ward  JA , DiLaura  G , Dolovich  S .  COVID-19 cases and deaths in federal and state prisons.   JAMA. 2020;324(6):602-603. doi:10.1001/jama.2020.12528 PubMedGoogle ScholarCrossref
Schnepel  K . COVID-19 in US state and federal prisons: December 2020 update. Accessed December 22, 2020.
National Academies of Sciences, Engineering, and Medicine.  Decarcerating Correctional Facilities During COVID-19: Advancing Health, Equity, and Safety. National Academies Press; 2020. doi:10.17226/25945
Pringle  JC , Leikauskas  J , Ransom-Kelley  S ,  et al.  COVID-19 in a correctional facility employee following multiple brief exposures to persons with COVID-19—Vermont, July–August 2020.   MMWR Morb Mortal Wkly Rep. 2020;69(43):1569-1570. doi:10.15585/mmwr.mm6943e1 PubMedGoogle ScholarCrossref
Hawks  L , Woolhandler  S , McCormick  D .  COVID-19 in prisons and jails in the United States.   JAMA Intern Med. 2020;180(8):1041-1042. doi:10.1001/jamainternmed.2020.1856 PubMedGoogle ScholarCrossref
Akiyama  MJ , Spaulding  AC , Rich  JD .  Flattening the curve for incarcerated populations—Covid-19 in jails and prisons.   N Engl J Med. 2020;382(22):2075-2077. doi:10.1056/NEJMp2005687 PubMedGoogle ScholarCrossref
Foster v Mici, No. SJ-2020-0212 (Mass 2020). Testimony of Carol Mici, Commissioner of the Department of Correction of Massachusetts. Accessed March 2, 2021.
ACLU of Massachusetts. Tracking COVID-19 in Massachusetts prisons and jails. Accessed July 8, 2021.
Massachusetts Department of Correction. DOC COVID-19 institution cell housing reports archives. Accessed July 8, 2021.
Massachusetts Department of Correction. Quarterly reports on prison capacity. Accessed July 8, 2021.
Dong  E , Du  H , Gardner  L .  An interactive web-based dashboard to track COVID-19 in real time.   Lancet Infect Dis. 2020;20(5):533-534. doi:10.1016/S1473-3099(20)30120-1 PubMedGoogle ScholarCrossref
Bureau of Justice Statistics. Census of State and Federal Adult Correctional Facilities (CCF, formerly CSFACF). Accessed July 8, 2021.
Lauer  SA , Grantz  KH , Bi  Q ,  et al.  The incubation period of coronavirus disease 2019 (COVID-19) from publicly reported confirmed cases: estimation and application.   Ann Intern Med. 2020;172(9):577-582. doi:10.7326/M20-0504 PubMedGoogle ScholarCrossref
Qin  J , You  C , Lin  Q , Hu  T , Yu  S , Zhou  X-H .  Estimation of incubation period distribution of COVID-19 using disease onset forward time: a novel cross-sectional and forward follow-up study.   Sci Adv. 2020;6(33):eabc1202. doi:10.1126/sciadv.abc1202 PubMedGoogle Scholar
McAloon  C , Collins  Á , Hunt  K ,  et al.  Incubation period of COVID-19: a rapid systematic review and meta-analysis of observational research.   BMJ Open. 2020;10(8):e039652. doi:10.1136/bmjopen-2020-039652 PubMedGoogle Scholar
Malloy  GSP , Puglisi  L , Brandeau  ML , Harvey  TD , Wang  EA .  Effectiveness of interventions to reduce COVID-19 transmission in a large urban jail: a model-based analysis.   BMJ Open. 2021;11(2):e042898. doi:10.1136/bmjopen-2020-042898 PubMedGoogle Scholar
Simpson  PL , Simpson  M , Adily  A , Grant  L , Butler  T .  Prison cell spatial density and infectious and communicable diseases: a systematic review.   BMJ Open. 2019;9(7):e026806. doi:10.1136/bmjopen-2018-026806 PubMedGoogle Scholar
Brown  KA , Jones  A , Daneman  N ,  et al.  Association between nursing home crowding and COVID-19 infection and mortality in Ontario, Canada.   JAMA Intern Med. 2021;181(2):229-236. doi:10.1001/jamainternmed.2020.6466 PubMedGoogle ScholarCrossref
Haney  C .  The psychological effects of solitary confinement: a systematic critique.   Crime and Justice. 2018;47(1):365-416. doi:10.1086/696041 Google ScholarCrossref
Brinkley-Rubinstein  L , Sivaraman  J , Rosen  DL ,  et al.  Association of restrictive housing during incarceration with mortality after release.   JAMA Netw Open. 2019;2(10):e1912516. doi:10.1001/jamanetworkopen.2019.12516 PubMedGoogle Scholar
Wildeman  C , Andersen  LH .  Solitary confinement placement and post-release mortality risk among formerly incarcerated individuals: a population-based study.   Lancet Public Health. 2020;5(2):e107-e113. doi:10.1016/S2468-2667(19)30271-3 PubMedGoogle ScholarCrossref
Reiter  K , Ventura  J , Lovell  D ,  et al.  Psychological distress in solitary confinement: symptoms, severity, and prevalence in the United States, 2017-2018.   Am J Public Health. 2020;110(S1):S56-S62. doi:10.2105/AJPH.2019.305375 PubMedGoogle ScholarCrossref
Kajeepeta  S , Mauro  PM , Keyes  KM , El-Sayed  AM , Rutherford  CG , Prins  SJ .  Association between county jail incarceration and cause-specific county mortality in the USA, 1987-2017: a retrospective, longitudinal study.   Lancet Public Health. 2021;6(4):e240-e248. doi:10.1016/S2468-2667(20)30283-8PubMedGoogle ScholarCrossref
Reinhart  E , Chen  DL .  Incarceration and its disseminations: COVID-19 pandemic lessons from Chicago’s Cook County jail.   Health Aff (Millwood). 2020;39(8):1412-1418. doi:10.1377/hlthaff.2020.00652 PubMedGoogle ScholarCrossref
Puglisi  LB , Malloy  GSP , Harvey  TD , Brandeau  ML , Wang  EA .  Estimation of COVID-19 basic reproduction ratio in a large urban jail in the United States.   Ann Epidemiol. 2021;53:103-105. doi:10.1016/j.annepidem.2020.09.002 PubMedGoogle ScholarCrossref
Altibi  AM , Pallavi  B , Liaqat  H ,  et al.  Characteristics and comparative clinical outcomes of prisoner versus non-prisoner populations hospitalized with COVID-19.   Sci Rep. 2021;11(1):6488. doi:10.1038/s41598-021-85916-w PubMedGoogle ScholarCrossref
Jiménez  MC , Cowger  TL , Simon  LE , Behn  M , Cassarino  N , Bassett  MT .  Epidemiology of COVID-19 among incarcerated individuals and staff in Massachusetts jails and prisons.   JAMA Netw Open. 2020;3(8):e2018851. doi:10.1001/jamanetworkopen.2020.18851 PubMedGoogle Scholar
Sundt  J , Salisbury  EJ , Harmon  MG .  Is downsizing prisons dangerous?: the effect of California’s Realignment Act on public safety.   Criminol Public Policy. 2016;15(2):315-341. doi:10.1111/1745-9133.12199 Google ScholarCrossref
Physicians for Human Rights. Praying for hand soap and masks: health and human rights violations in US immigration detention during the COVID-19 pandemic. Published January 2021. Accessed May 1, 2021.
Lopez  WD , Kline  N , LeBrón  AMW ,  et al.  Preventing the spread of COVID-19 in immigration detention centers requires the release of detainees.   Am J Public Health. 2021;111(1):110-115. doi:10.2105/AJPH.2020.305968 PubMedGoogle ScholarCrossref
If you are not a JN Learning subscriber, you can either:
Subscribe to JN Learning for one year
Buy this activity
If you are not a JN Learning subscriber, you can either:
Subscribe to JN Learning for one year
Buy this activity
With a personal account, you can:
  • Access free activities and track your credits
  • Personalize content alerts
  • Customize your interests
  • Fully personalize your learning experience
Education Center Collection Sign In Modal Right

Name Your Search

Save Search
With a personal account, you can:
  • Track your credits
  • Personalize content alerts
  • Customize your interests
  • Fully personalize your learning experience

Lookup An Activity



My Saved Searches

You currently have no searches saved.

With a personal account, you can:
  • Access free activities and track your credits
  • Personalize content alerts
  • Customize your interests
  • Fully personalize your learning experience
Education Center Collection Sign In Modal Right