Estimating the Clinical and Economic Outcomes of Universal Varicella and Herpes Zoster Vaccination in Belgium Using a Dynamic Transmission Model With Dynamic Population

OBJECTIVES: Varicella zoster virus is responsible for varicella (chicken pox) and herpes zoster (HZ; shingles). We aimed to evaluate the clinical and economic outcomes (for both varicella and HZ) of two-dose universal varicella vaccination (UVV) in Belgium with and without concurrent HZ vaccination.

METHODS: A previously published dynamic transmission model with dynamic population age structure was adapted to Belgium. The UVV strategy comprised two-dose varicella vaccination at 1- and 8-years (95% and 90% coverage, respectively) with one-dose varicella catch-up vaccination at 8-years (70% coverage, duration of one year). Additionally, an HZ vaccination strategy (vaccination at 60-years with 50% coverage) was considered. The latest real-world evidence on exogenous boosting was used in our model. The UVV, HZ, and UVV+HZ strategies were compared against no-vaccination. Outcomes were estimated for a 50-year time-horizon (2023-2073). Annual discounting of 3% and 1.5% were applied to costs (in 2023 Euros) and quality-adjusted life-year outcomes, respectively.

RESULTS: Under the UVV strategy, cumulative varicella cases, varicella related hospitalizations, varicella-related mortality and HZ cases decreased by 90.7%, 89.3%, 58.2% and 0.8%, respectively, versus no vaccination. Under the UVV+HZ strategy, cumulative HZ cases decreased by 14.3% versus no vaccination. Under both payer and societal perspectives, the cost-effectiveness frontier comprised the no vaccination, UVV, and UVV+HZ strategies; the HZ strategy was weakly dominated by UVV and UVV+HZ strategies. Under the payer perspective, the UVV strategy was cost-effective in Belgium at a willingness to pay (WTP) threshold of 1xGDP (€36,860) (incremental cost-effectiveness ratio [ICER]: €20,812), however, the UVV+HZ strategy was not cost-effective (ICER: €55,236). Similarly, under the societal perspective, the UVV strategy was cost-effective at a 1xGDP WTP threshold (ICER: €1,416) and the UVV+HZ strategy was not (ICER: €50,728).

CONCLUSIONS: Two-dose UVV significantly reduced burden of varicella and was cost-effective in Belgium compared to no vaccination. Concurrent UVV and HZ vaccination was not cost-effective in Belgium.