Table 1.
Epidemiological and quality of life (QALY) parameters of the economic model. We report the base case values and the standard deviations, taken either from the literature or from administrative data, the shapes of the prior distribution, the 95% CI from the posterior distribution of the parameters, and the source of the base case values
| Parameter | Base case values | Standard deviations | Prior Distribution | 95% CI Posterior distribution | Source |
|---|---|---|---|---|---|
| Epidemiological parameters | |||||
| Proportion of HZ cases developing PHNc | 0.049 (by age) | 0.0023 (by age) | Beta | – | [2] |
| Hosp. rate for natural varicella (NV) per model TI/PI (per 1000 cases) | 2.35/2.36 (by age) | 0.61/0.62 (by age) | Beta | – | Estimatea |
| Breakthrough varicella (BV) vs. NV hosp. rate | 0.25 | 0.05 | Beta | [0.16–0.35] | [58, 59] |
| Hosp. rate for HZ per model TI/PI (per 1000 cases) | 13.60/13.12 (by age) | 4.49/4.63 (by age) | Beta | – | Estimatea |
| Hosp. rate for PHN per model TI/PI (per 1000 cases) | 41.55/40.77 (by age) | 9.53/10.39 (by age) | Beta | – | Estimatea |
| Case fatality rate for NV (per 1000 hospitalised) | 4.01 (by age) | 2.98 (by age) | Beta | – | Estimateb |
| BV vs. NV case fatality rate | 0.005 | 0.0022 | Beta | [0.002–0.01] | [59, 60] |
| HZ-PHN case fatality rate (per 1000 hospitalised) | 12.70 (by age) | 5.43 (by age) | Beta | – | Estimateb |
| No. GP consultations per NV case | |||||
| < 14 years | 2 | 0.2 | Gamma | [1.63–2.43] | [59] |
| ≥ 15 years | 1 | 0.2 | Gamma | [0.64–1.43] | [59] |
| No. GP consultations per BV case | 0.5 | 0.05 | Gamma | [0.41–0.60] | [59] |
| Quality of life measures | |||||
| Overall weighted health state index (EQ-5Dindex) | 0.84 (by age) | 0.21 (by age) | Beta | [61] | |
| Weighted health state index varicella | |||||
| < 14 years | 0.81 | 0.031 | Beta | [0.76–0.86] | [31] |
| ≥ 15 years | 0.73 | 0.025 | Beta | [0.68–0.78] | [62] |
| Prob. severe NV cases | 0.65 | 0.0063 | Beta | [0.64–0.66] | [63] |
| Prob. severe BV cases | 0.25 | 0.011 | Beta | [0.23–0.27] | [63] |
| Reduction in QALY loss Mild vs. severe varicella cases |
0.25 | 0.10 | Beta | [0.08–0.47] | [48] |
| QALY loss HZ | |||||
| 20 years | 0.022 | 0.0018 | Beta | [0.019–0.026] | [48] |
| 40 years | 0.031 | 0.0030 | Beta | [0.026–0.037] | [48] |
| 60 years | 0.064 | 0.0082 | Beta | [0.049–0.081] | [48] |
| 80 years | 0.19 | 0.030 | Beta | [0.14–0.25] | [48] |
aAverage number of hospitalisations by age due to varicella, HZ, and PHN (Hospital Discharge Register, 2001–2012) divided by the predicted pre-vaccination incidence generated by the epidemiological model. PHN incidence is derived by multiplying the estimated HZ incidence by the probability of HZ cases developing PHN [2]
bAverage number of deaths by age due to varicella (Italian National Health Institute, 2001–2012) and HZ (European Union detailed mortality database, 2001–2012) divided by the respective estimates of the hospitalisation rates
cPHN cases lasting at least 3 months