Table IV.
Model Inputs for the USA Model
| Model input (symbol) | Best estimate | Source | Notes |
|---|---|---|---|
|
| |||
| Number of subpopulations | 1 | Model intended to reflect average conditions in the USA | |
| Number of age groups | 11 | 0–2; 3–5; 6–11 month; v1; 2; 3; 4; 5–9; 10–14; 15–19*; ≥ 20 years* | |
| Number of mixing age groups | 3 | 0–4; 5–14; ≥15 years | |
| Year when model run-up starts | 1880 | ||
| Year when R0 seasonality starts | 1900 | ||
| Year when die-out first allowed | 1955 | ||
| Average basic reproductive number (R0) (PV1) | 5 | Fitted within range for highest tier (Table III); PV2&3 according to ratios in Table I | |
| Proportional change in R0 due to seasonality (α) | 0.05 | Lower value than previously assumed to avoid significant long-term oscillations that should cancel out for a large USA population | |
| Day of seasonal peak in R0 (pd) | 212 (July 31) | ||
| Proportion of contacts reserved for individuals within the same mixing age group () | 0.35 | For simplicity, assume equal values for each mixing age group | |
| Proportion of transmissions via oropharyngeal route () | 0.8 | 19 | Fitted within range of expert assessments(19) and using value for the Netherlands as upper bound (Table V) |
| Per-dose take rate (tr) (PV1;PV2:PV3) | Fitted within range for highest tier (Table III); IPV take rates based loosely on field efficacy of IPV against poliomyelitis in the USA(55) in 1954 | ||
| - IPV (Salk) | 0.5;0.6;0.5 | ||
| - mOPV | 0.9;0.95;0.9 | ||
| - tOPV | 0.65;0.75;0.55 | ||
| Assumptions about IPV (Salk) campaigns 1955–1963 | 9,71,72 | Doses and coverage based on total IPV doses distributed by mid-1962 and immunization surveys by age; see Appendix A4 for | |
| - Annual cumulative coverage, age 0–19 years | Time series | coverage values used | |
| - Relative annual cumulative coverage, age ≥ 20 vs. 0–19 years Assumptions about mOPV campaigns 1962–1964 |
0.55 | 9,71,72 | Doses and coverage based on total mOPV doses distributed (16% wastage assumed) by 1965 and immunization surveys by age, adjusted for known underestimation; campaigns modeled as annual 1-day events on day 60 of each year, with each round effectively reaching 1/3rd of the eventually covered population |
| - Doses per covered person | 1 of each type | ||
| - Cumulative coverage, age 0–19 years | 0.8 | ||
| - Cumulative coverage, age ≥ 20 years | 0.4 | ||
| Routine coverage with 3 polio vaccine doses, and partial coverage | Time series 1965–96 | 9,71,72 | Partial coverage based on DTP1 and DTP3 data; see Appendix A4 for all values used |
| Characterization of routine IPV (Salk) (1958–1964) or tOPV (1965–1996) immunization | 73,74 | See methods for calculation of average effective vaccination coverage at each age | |
| - Cumulative effect of first 2 doses at age (months) | 3 | ||
| - Third dose at age (months) | 6 (<1967) or 12 (≥1967) | ||
| - Booster dose at age (years) | 5 | ||
| - Coverage of IPV (Salk) booster doses | 0.8 | ||
| - Coverage of booster tOPV doses | 0.9 | ||
Acronyms: DTP1(3) = coverage with 1 (3) dose(s) of difteria-tetanus-pertussis vaccine by age 1; IPV = inactivated poliovirus vaccine; mOPV = monovalent oral poliovirus vaccine; PV(1,2,3) = poliovirus (type 1, 2, or 3, respectively); tOPV = trivalent oral poliovirus vaccine; USA = United States of America
*
Age groups marked with an asterisk indicate age groups that count towards determining the fraction of newborns that receive maternal antibodies, based on the immune fraction in those age groups (see Appendix A1).