Table 1.
Modeling Parameters and Assumptions.
| Parameter | Value | Source(s) |
|---|---|---|
| Basic reproductive number (R0) | 3.32 | Alimohamadi et al. (2020) |
| Initial susceptible population | 274,165,495 (<65) 54,074,028 (65+) |
U.S. Census Bureau (2019) |
| Initial infections on January 1, 2020 | 0 | Assumed |
| Daily infected international arrivals, January and February 2020 | 30 (January 2020) 45 (February 2020) |
Calibrated based on real-world data |
| Daily infected international arrivals, March 2020 through June 2022 | between 0 and 947 | Calculated based on I-94 Visitor Arrival Program; Bureau of Transportation Statistics 2019–2020 (Bureau of Transportation Statistics, 2021) |
| Latent period (pre-infectious) | 2.5 days | Vardavas et al. (2021); Rhee et al. (2021) |
| Infectious period (asymptomatic, pre-symptomatic and symptomatic) | 7.5 days | CDC (2021b); Rhee et al. (2021) |
| Hospitalization rate (h) | 2.90% (<65) 21.21% (65+) |
CDC (2021c) |
| Age-specific infection fatality rate (IFR) | 0.0969% (<65) 3.3049% (65+) |
O'Driscoll et al. (2021) |
| Vaccine effectiveness (VE) | 90% | CDC (2021a) |
| Proportion of population willing to vaccinate | 73.54% (<65) 84.96% (65+) |
Kapteyn and Gutsche (2021) weighted by American Community Survey (U.S. Census Bureau, 2019) |
| IFR Multiplier during peak hospitalization periods | Under 75,000 hospitalizations: 1.00 Over 75,000 hospitalizationsa: 1.20 Over 125,000 hospitalizationsb: 1.30 |
Based on Rossman et al. (2021) |
| Seasonality adjustment coefficient | 0.75–1.27 | The effective reproductive rate is a factor of the basic reproductive number and the seasonality coefficient. Based on Gavenčiak et al. (2021), see Appendix 5.A.6 |
a
Based on the onset of highest hospitalization counts in Fall (2020) and Summer 2021, which resulted in local shortages of intensive care beds and personnel.
b
Based on the reported peak of hospitalizations when many states were running out of intensive care beds and personnel to provide the highest-quality care.