P-627. Modeling the Clinical and Economic Impact of Increasing Varicella Vaccination Coverage in Panama

Abstract Background Panama implemented two-dose universal varicella vaccination (UVV) in 2018. First-dose vaccination coverage rates (VCRs) declined from 91% (2018) to 70% (2021) during the COVID-19 pandemic. We quantified the clinical and economic impact of increasing UVV VCRs over a 10-year time horizon. Methods A previously published age-structured dynamic transmission model was adapted to Panama using country-specific demographic, healthcare resource use, cost, and epidemiological data or comparable proxy. Four UVV strategies (1st dose: 15 months; 2nd dose: 4 years) were evaluated, with 1st dose VCR assumed to be (A) 70% (status quo), (B) 80%, (C) 90%, and (D) 95% for the strategies A-D (Table 1). Second dose VCR was assumed to be 50% of first dose VCR. Outcomes were evaluated over a 10-year time horizon (2022-2031) and included cumulative varicella cases, outpatient cases, hospitalizations, deaths, payer (direct) costs, and societal (direct and indirect) costs. Costs were reported in 2023 USD with 3% annual discounting. Results Under the status quo (strategy A), we estimated 232,381 cumulative varicella cases, 159,123 outpatient cases, and 7,320 hospitalizations over 10 years, resulting in total payer and societal costs of $29,335,329 and $36,893,235, respectively. Increasing 1st dose/2nd dose VCR from 70%/35% (Strategy A) to 80%/40% (Strategy B) will avert approximately 3.6% of varicella cases, 4% of hospitalizations, and 1.8% of deaths. Increasing VCR to 90%/45% (Strategy C) will avert 6.8% of all cases, 7.7% of hospitalizations, and 3.5% of deaths compared to reference Strategy A. The impact of increasing VCRs to 95%/47.5% (Strategy D) resulted in a further reduction in varicella cases by about 20% more than Strategy C. Strategies B-D increased payer costs by 2%-6% ($0.02-$0.04 per person per year [PPPY]) and societal costs by 1%-4% ($0.01-$0.03 PPPY) over the 10-year time horizon versus reference strategy A (Figure 1). Conclusion Increasing UVV VCRs compared to the status quo will result in improved clinical outcomes with marginal increases in payer and societal costs. Disclosures Colleen Burgess, MS, Merck & Co., Inc., Rahway, NJ, USA: Contractor Salome Samant, MBBS, MPH, Merck & Co., Inc., Rahway, NJ, USA: Employee- earned salary and own stock|Merck & Co., Inc., Rahway, NJ, USA: Stocks/Bonds (Public Company) Luciana Hirata, PhD, Merck & Co., Inc., Rahway, NJ, USA.: I am an employee of MSD subsidiary of Merck & Co., Inc., Rahway, NJ, USA. and may hold stock or stock options in Merck & Co., Inc. Cintia I. Parellada, MD, PhD, Merck & Co., Inc: Employee|Merck & Co., Inc: Stocks/Bonds (Private Company) Manjiri D. Pawaskar, PhD, merck: employee|merck: Stocks/Bonds (Public Company) John C. Lang, PhD, MSc, MSc, BSc, Merck & Co., Inc.: Stocks/Bonds (Private Company)|Merck Canada Inc.: Employee