Table 1.
Symbol definitions, approximate values, and sources.
| Symbol | Meaning | Values | Source |
|---|---|---|---|
| pi | Proportions of Infectious people who are Asymptomatic (or Symptomatic, 1 – pi) | Tbl 2 | Clark, et al. 2020 |
| qi | Proportions not receiving booster doses when eligible | ‡ | |
| k | Per capita rate of progression from Exposed, E to Asymptomatic, Ia or Pre-symptomatic, Ip (1/3 to 1/5 days depending on variant) | 1/4 dys | He, et al. 2020 |
| ξ,γs→h | Per capita rates of progression from Pre-symptomatic, Ip to Symptomatic, Is and Symptomatic to Hospitalized, Ih | 1/2 dys | He, et al. 2020 |
| γa | Per capita rate at which people with Asymptomatic infections recover (become no longer infectious) | 1/7 | |
| γs | Per capita rate at which people with Symptomatic infections who are not hospitalized recover (again, become no longer infectious) | 1/5 dys | He, et al. 2020 |
| γh | Per capita rate at which Hospitalized people recover (NB: may well differ from the discharge rate) | 1/10 dys | |
| θw | Proportions of Symptomatic people who Recover (or Die, 1 – θw), which may differ among those Hospitalized (w = s, h) | Tbl 2 | Levin, et al. 2020 |
| δi | Proportions of Symptomatic people who are Hospitalized (proportions with 2+ co-morbidities) | Tbl 2 | Clark, et al. 2020 |
| χ1i, χ2i, χ3i, | Per capita immunization rates, where vi is the coverage attained during period δt | ‡ | |
| ∊1, ∊2, ∊3 | Probabilities of protection upon contact with infectious people 14 or more days after first, second, and booster doses | 0.93 | El Sahly, et al. 2021 |
| ω, ωv | Per capita rates at which infection- and vaccine-induced immunity is lost | 1/365 dys | |
| ci | Proportion of people complying with social distancing or mask wearing recommendations (compliance) | Tbl 2 | Jones et al., 2021 |
| bS, bI | Reduced susceptibility or infectivity (efficacy) by virtue of complying with physical-distancing where possible and mask-wearing otherwise | 0.31 | Estimated |
| ηw | Scaling constants (w = a, p, h) representing the infectivity of Iia, Iip, Iih relative to Iis | 0.5, 1.25, 0.1 |
Notes: We assume that people with asymptomatic infections are less infectious than those with symptomatic ones, but that their sojourns are the same. ‡Calculated from reports summarized on https://data.cdc.gov/.