Table 1. Epidemiological model parameters.
| Parameter | Value | Reference |
|---|---|---|
| Demographic | ||
| Birth cohorts (1975–2019)a | Range (49 937–68 762) | [13] |
| Infant mortality (<1 year) per 1000 (1975–2019)a | Range (2.33–10.79) | [13] |
| Mortality 1–4 years per 1000 (1975–2019)a | Range (0.67–0.12) | [13] |
| Mortality 5–69 years per 1000 (1975–2019)a | Range (2.20–3.92) | [13] |
| Mortality 70+years per 1000 (1975–2019)a | Range (56.30–68.33) | [13] |
| Net immigration (1975–2019)a | Range (1 453–47 343) | [13] |
| Population January 1, 1975 | 3 972 990 | [13] |
| Natural history | ||
| Mean duration of maternal immunity (days) | 102 | [28, 29] |
| Mean duration of latency period (days) | 0.5 | [16, 17] |
| Mean duration of infectious period (1st; 2nd; 3rd and later) (days) | 7; 3.5; 1.75 | [30, 31] |
| Relative infectivity (1st; 2nd; 3rd and later) | 1; 0.5; 0.2 | Author assumption |
| Relative susceptibility (1st; 2nd; 3rd and later) | 1; 0.62; 0.40 | [19] |
| Mean duration of natural immunity (years) | 1 | [15, 20–22] |
| Proportion with RVGE/(severe RVGE) (1st; 2nd; 3rd and later) | 0.47; 0.25; 0.24 | [19] |
| Proportion severe RVGE (1st; 2nd; 3rd and later) | 0.13; 0.04; 0 | [19] |
| Vaccination | ||
| Proportion with RVGE (among children with no previous infection)b | Uniform random (0.225–0.375) | [26] |
| Proportion severe RVGE (among children with no previous infection)b | Uniform random (0.01–0.04) | [26, 27] |
| Mean duration of vaccine–induced immunity (years) | 2 | [23, 25, 27, 32] |
| Coverage (max after introduction) | 0.947 first dose (baseline); 0.877 second dose | [11] |
| Healthcare and deaths in children under five years of age | ||
| Proportion of severe RVGE seeking primary healthcare | Uniform random (0.95–1.0) | Author assumption |
| Calibration of inpatient hospital contacts (2014) | Random Norm (1226, 86.5) | [9] |
| Calibration of outpatient hospital contacts (2014) | Random Norm (695, 28.3) | [9] |
| Calibration of fatal inpatient hospital contacts (2014) | Random Norm (4.218e–4, 0.35e–4) | [9] |
| Fitted parameter values | ||
| Transmission parameter (β0) | 0.48312 | |
| Seasonal forcing (β1)c | 0.0433 | |
| Phase angle (φ)c | 0.6191 | |
| Relative mixing, children <12 months (mix_1y) | 0.4803 | |
| Relative reporting rate children >2.5 years (rep2,5y) | 0.4629 |
a) Only minimum and maximum values of the demographic parameters are listed. All simulations were performed using the same set of demographic parameters.
b) Proportions estimated to provide a vaccine efficacy of 0.93 (95% CI 0.87–0.98) against severe disease and 0.60 (95% CI 0.51–0.70) against mild disease. Vaccine efficacy calculated for children with no previous natural infection.
c) Transmission rate modelled as: β0 (1+β1 (sin 2πt/ (365+φ))).