Background
Methods and materials
Data
Statistical methods
Per capita rates
Correlations and pair-wise comparisons
Relationship between per capita rates to prison security level
Assessing the effect of decarceration in reducing outbreak size
Results
Correlations between per capita rates
Pairwise comparison of per capita rates in outbreaks in staff, incarcerated individuals, and the community
Mean difference | Paired Student’s t-test p-value | Risk Ratio | |
---|---|---|---|
Overall | |||
pinmate – pstaff | [0.01,0.14] | 0.025 | 1.22 |
pinmate – pcounty | [0.24,0.38] | < 0.001 | 4.47 |
pstaff – pcounty | [0.18,0.29] | < 0.001 | 3.89 |
Summer wave | |||
pinmate – pstaff | [-0.02,0.04] | 0.53 | 1.15 |
pinmate – pcounty | [0.02,0.09] | < 0.001 | 4.32 |
pstaff – pcounty | [0.03,0.06] | < 0.001 | 3.36 |
Winter wave | |||
pinmate – pstaff | [0.01,0.12] | 0.030 | 1.24 |
pinmate – pcounty | [0.19,0.32] | < 0.001 | 4.51 |
pstaff – pcounty | [0.14,0.25] | < 0.001 | 4.03 |
Relationship of per capita rates to prison security level
Estimate | |
---|---|
Log(community per capita) | + 1.221(0.179)*** |
Factor: Minimum security | -2.264(1.049) |
Factor: Low security | + 2.921(0.758)*** |
Factor: Medium security | + 2.037(0.785)** |
Factor: High security | + 1.582(0.856)* |
Effect of decarceration on per capita rates in incarcerated individuals, staff, and community
Discussion
Limitations
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Rather than publishing total number of newly identified cases per some time-period (like day, week or month), the BoP instead publishes the number of people who have tested positive (and are still positive), along with the number recovered and number dead, and only does so sporadically and not at evenly spaced time points. The mismatch between having to compare prevalence in the prison populations to incidence in the community populations was a relatively minor complication to this analysis because we examine relatively long time periods. But the incidence vs prevalence reporting differences seriously complicate any potential future analysis of short term temporal trends in the data because incidence data lag that of prevalence by half the average infectious period. In addition, the daily reporting of community data, and irregular reporting of BoP data would also seriously complicate such an analysis. In general, the BoP surveillance data do not exhibit good epidemiological and public health practices in infectious disease reporting standards [1, 33]. Greater governmental oversight and guidance on infectious disease surveillance and reporting for such institutions is warranted to make the data more useful towards informing outbreak control, including standardization of testing protocols across institutions.
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While detailed temporal information is available on the incarcerated population per prison, estimates of staff come from one time point in mid 2020. This potentially creates some unreliability of our staff per capita rate assessments, if in fact the staff population sizes significantly varied over the time frame under consideration.
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Information of race and ethnicity of incarcerated individuals in the federal prisons, including those testing positive for SARS-COV-2 are not available, but are potentially an important factor to take into account in any analysis of transmission disparities.
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The number of SARS-COV-2 cases in the incarcerated population and staff is published at the prison level, but for prisons that are part of larger multiple-security-level complexes, the BoP only publishes staffing information for the entire complex. Thus, per capita rates for staff could not be computed for those prisons, and they had to be excluded for parts of the analysis examining staff per capita rates. Should that data be made available, it would increase the sensitivity of the analysis to detecting potential relationship of staff per capita rates of infection to factors like security level.
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The BoP does not publish the number of tests performed, only the total number of positive tests (and deaths), and it is unclear what surveillance protocols were in place, and whether these differed by prison [21]. For example, it is unknown whether regular random testing of the incarcerated population or staff was performed to identify asymptomatic cases, or whether testing was solely performed on symptomatic individuals, or even just upon request.