Table 1.
Model parameters, including distributions used in the probabilistic sensitivity analysis
| Parameter | Mean (SE) | Distribution | Source and notes |
|---|---|---|---|
| R0 | 5.08 (1.41) | log-normal | [23] |
| Percentage reduction in R0 due to shielding and cohorting | 40% | beta | [17] |
| Vaccine efficacy against infection – first dose | 60% (10–70%) | beta | [24, 25] |
| Vaccine efficacy against infection – second dose | 80% (10–90%) | beta | |
| Vaccine efficacy against disease – first dose | 60% (50–90%) | beta | |
| Vaccine efficacy against disease – second dose | 85% (50–95%) | beta | |
| Waning of vaccine immunity | Vaccine efficacy falls by 19% (95%CI 8%-34%) over six months | beta | [26] |
| Duration of natural immunity | 16% (95%CI 13–19%) reduction in immunity over one year | beta | [27] |
| Staff turnover | 8.4% per year (0.1%) | beta | [28]. In-migration assumed to be equal to out-migration |
| New people incarcerated | 0.60% per day (0.17%) | beta | [29]. Based on new receptions into local male prisons. In-migration assumed to be equal to out-migration |
| Number vaccinated per day | 20 | fixed | Assumption based on insights of author from HMPPS (O’Mara) |
| Community incidence | 0.001 per 10,000 people per day (0.0015) | fixed | [30] |
| [31] | |||
| Population size of those incarcerated | 820 | fixed | [29]. HMPPS Prison Population Tool. Mean for local male prisons |
| Staff population size – Staff Group 1 | 70 | fixed | [28]. Mean for local male prisons |
| Staff population size – Staff Group 2 | 315 | fixed | [28]. Mean for local male prisons |
| Age distribution of people who are incarcerated | fixed | [29]. HMPPS Prison Population Data Tool, December 2020. Mean for local male prisons | |
| Age distribution of staff | fixed | [32] | |
| Contact patterns—Staff Group 1 | 80% of contacts with other staff in Group 1; 20% with Staff Group 2 | fixed | Internal HMPPS correspondence |
| Contact patterns—Staff Group 2 | 20% of contacts with Staff Group 1; 40% with other staff in Group 2; 40% with people who are incarcerated | fixed | Internal HMPPS correspondence |
| Contact patterns—individuals who are incarcerated | 40% of contacts with Staff Group 1; 60% of contacts with other people who are incarcerated | fixed | Internal HMPPS correspondence |
| Quality-Adjusted Life Year (QALY) loss per symptomatic case | 0.008 (4.7 × 10–5) | beta | [33] |
| QALY loss per non-fatal hospitalisation | 0.018 (0.0018) | beta | [34] |
| QALY loss per non-fatal ICU admission | 0.154 (0.0304) | beta | [35] |
| QALY loss per fatality—staff | Age-dependent (SMR = 2, qCM = 0.9, discount rate = 0.35) | [36] | |
| QALY loss per fatality – people who are incarcerated | Age-dependent (SMR = 2.3, qCM = 0.9, discount rate = 0.35) | [36, 37] | |
| QALY loss per Adverse Event Following Immunisation (AEFI)—minor | 1/365.25 | fixed | [20] |
| Frequency of AEFI—minor | Age-dependent | fixed | [38] |
| QALY loss per AEFI—fatal | Age-dependent (SMR = 2, qCM = 0.9, discount rate = 0.35) | fixed | [36] |
| Frequency of AEFI—fatal | 0.18 × 3/1000000 | fixed | [39, 40] |
| Lateral Flow Device (LFD) sensitivity | 0.8 (0.125) | beta | [41] |
| LFD uptake among prison staff | 0.508 (0.107) | beta | [9] |
| Vaccine coverage | 0.675 (0.148) | beta | [42] |