Modeling the Effects of Improving Varicella Vaccination Coverage Rates on Clinical and Economic Outcomes in Peru Over a 10-Year Time-Horizon

OBJECTIVES: Peru implemented a one-dose universal varicella vaccination program in 2018, however, vaccination coverage rates (VCRs) remain low (i.e., 66% in 2022). We aimed to estimate the clinical and economic impact of increasing varicella VCR over 10-year time horizon (2023-2033).

METHODS: A previously published dynamic transmission model for varicella was adapted to Peru using country-specific demographic, healthcare resource use, cost, and epidemiological data. Our reference strategy assumed a constant VCR of 66%. Comparator strategies comprised: increasing VCR to (A) 80%, (B) 85%, and (C) 90% over 1 year and increasing VCR to 85% over (D) 2 years and (E) 5 years. Outcomes comprised cumulative varicella cases, outpatient cases, inpatient cases, and payer (i.e., direct) and societal (i.e., direct and indirect) costs per person per year (PPPY). Costs were reported in 2023 United States dollars (USD) and were discounted at 5% annually.

RESULTS: Under the reference strategy (66% VCR from 2023-2033) we estimated 2,161,267 varicella cases, 211,489 outpatient cases, 46,989 inpatient cases, and 77 deaths. Payer and societal costs were 0.39 USD PPPY and 0.43 USD PPPY, respectively. Increasing VCR over a 1-year period resulted in reductions in varicella cases, outpatient cases, and inpatient cases of approximately (A) 16%, (B) 21%, and (C) 24% (Figure 1); deaths were reduced by (A) 9%, (B) 11%, and (C) 13%. When increasing VCR to 85%, the greatest reductions in clinical outcomes occurred over the 1-year period (i.e., Strategy B) versus the 2- and 5-year periods (excluding deaths: [D] 19%, [E] 13%; deaths: [D] 10%, [E] 7%). For all strategies, cost increases were at most 0.08 USD PPPY.

CONCLUSIONS: Increasing varicella VCR resulted in better clinical outcomes and, in absolute terms, a small increase in costs. While all strategies improved clinical outcomes, increasing the VCR within one year, compared to 2 and 5 years, showed greater benefits.