Modeling the effects of improving varicella vaccination coverage on clinical and economic outcomes in Peru

Despite the implementation of a single-dose universal varicella vaccination program in Peru since 2018, vaccination coverage rates (VCRs) remain low, with a VCR of 66% as of 2022. We employed a dynamic transmission model (DTM) to evaluate the impact of increasing varicella VCRs in Peru. We parameterized a previously published DTM with publicly available demographic, healthcare resource use, cost, and epidemiological data inputs specific to Peru (or suitable regional proxy), including Peruvian varicella VCRs up to 2022. We modeled six single-dose UVV strategies over 10 years (2023-2032) that increased VCRs to 80-90% over 1-, 2- or 5-year periods, compared with the reference strategy assuming the continuation of the current VCR of 65.6%. Clinical and economic outcomes were reported; economic outcomes were reported in 2023 USD with 5% annual discounting. Parameter uncertainty was evaluated through probabilistic and deterministic sensitivity analyses. All six strategies with increased VCR resulted in 13%-25% fewer varicella cases, and 13%-24% fewer outpatient and inpatient cases, over 10 years, compared to continuing the current varicella VCR, with shorter VCR ramp-up periods resulting in more clinical outcomes averted. However, this led to a 12%-21% ($0.05-0.08 per person per year) increase in costs from the payer perspective. The PSA indicated that model results were robust to parameter uncertainty. Increasing varicella VCR led to improved clinical outcomes, with small increase in costs. Improving VCR at faster rates leads to better clinical outcomes relative to the reference strategy at a small per-capita cost increase.