OBJECTIVES: This study aims to evaluate the cost-effectiveness of nirsevimab, a long-acting monoclonal antibody prophylaxis preventing respiratory syncytial virus (RSV)-associated medically attended low respiratory tract infection (MA-LRTI) in infants, compared with the standard of care (SoC) in South Korea.

METHODS: We performed a cost-effectiveness analysis using a static decision-tree-model from a societal perspective for infants under one year old and children vulnerable to RSV under 24 months in South Korea. Health events included emergency room visit, hospitalization, intensive care unit and medical ventilation use, outpatient visits and death. The model compared nirsevimab with SoC (palivizumab for high-risk infants), using a one-season time-horizon and a 4.5% annual discount rate. We considered RSV seasonality and monthly birth population rates to estimate the targeted subgroups and their probability of RSV exposure. Health states and quality-adjusted life years (QALYs) of RSV-related MA-LRTI were defined through a systematic literature review. Probabilities of each node in the decision-tree model were derived from national claims data of the Health Insurance Review and Assessment Service from 2017 to 2021. Costs were estimated using the macro-costing approach and 2023 average euro exchange rate. The cost-effective prices were defined using 1 and 1.5 Gross Domestic Product (GDP) per capita as willingness-to-pay thresholds (WTPT) per QALY gained. Deterministic and probabilistic sensitivity analyses were also performed to inform decision uncertainty.

RESULTS: The cost-effective price range was observed for the birth cohort between €412, using 1 GDP WTPT, and €485 at 1.5 GDP WTPT. The incremental cost-effectiveness ratio (ICER) calculated at the median price of this range, which is €450, amounted to €38,526/QALY. Subgroup and sensitivity analysis with these prices showed that the uncertainty was mainly linked to epidemiological and population parameters.

CONCLUSIONS: Nirsevimab is estimated to be a cost-effective prophylaxis against RSV for infants in South Korea with robust ICER results despite some parameter uncertainties.