# Modeling the clinical and economic impact of universal varicella vaccination in Belgium with dynamic population

## TL;DR

The study evaluates the impact of universal varicella vaccination in Belgium, showing it can significantly reduce disease burden and be cost-effective.

## Contribution

The study introduces a dynamic population model to assess the clinical and economic impact of universal varicella vaccination in Belgium.

## Key findings

- Cumulative varicella incidence, hospitalizations, and deaths decreased by 91%, 89%, and 61%, respectively.
- Strategy 0 had an incremental cost-effectiveness ratio of €11,260 under the payer perspective.
- Total costs decreased by €17,524,487 under the societal perspective.

## Abstract

Although universal varicella vaccination (UVV) significantly reduces morbidity and mortality, it has not been implemented in Belgium. We evaluated the clinical and economic outcomes of two-dose UVV in Belgium. A previously published dynamic transmission model with dynamic population age structure was adapted to Belgium. The base case UVV strategy (Strategy 0) consisted of routine two-dose varicella vaccination at ages 1 year (vaccine coverage rate [VCR] = 95%) and 8 years (VCR = 90%), catch-up one-dose varicella vaccination at 8 years (VCR = 70%, 1-year duration), and routine two-dose herpes zoster (HZ) vaccination at 60 years (VCR = 50%). Alternative vaccination strategies were evaluated and reported. The reference strategy consisted of routine two-dose HZ vaccination only. Outcomes were estimated for a 50-year time-horizon. Annual discounting of 3% and 1.5% were applied to costs (in 2023 Euros) and quality-adjusted life-year outcomes, respectively. Under Strategy 0, cumulative varicella incidence, hospitalizations, and deaths decreased by approximately 91%, 89%, and 61% respectively. A transient increase in HZ incidence (that peaked in 2032 at +3% versus the reference strategy) was observed, however, cumulative HZ cases decreased by 3% over 50 years. Under the payer perspective, Strategy 0 had an incremental cost-effectiveness ratio of €11,260. Under the societal perspective, Strategy 0 resulted in cost savings, with total costs decreasing by €17,524,487. UVV can significantly reduce the burden of varicella with marginal impact on HZ cases and be cost-effective in Belgium versus routine HZ vaccination only.