Economic evaluation of a bivalent respiratory syncytial virus prefusion F vaccine for maternal vaccination in Sweden: cost-effectiveness and budget impact

Aims To compare the clinical and economic outcomes of three infant RSV prevention strategies, monoclonal antibody prophylaxis with nirsevimab alone, maternal RSVpreF vaccination alone, and maternal RSVpreF vaccination with complementary nirsevimab versus no intervention in Sweden, to estimate cost-effectiveness and budget impact.Methods A population-based, multi-cohort Markov model followed 12 monthly birth cohorts from birth to 1 year with age- and season-specific RSV risks. Three seasonal (October–February) strategies (87% uptake) were evaluated versus no intervention: monoclonal antibody prophylaxis with nirsevimab alone; maternal RSVpreF vaccination alone; and maternal RSVpreF vaccination with complementary use of nirsevimab for infants not protected via maternal vaccination. Outcomes included RSV outpatient visits, hospitalizations, deaths, costs (healthcare- and societal), Quality-Adjusted Life Years (QALYs), and Incremental Cost-Effectiveness Ratios (ICERs). Scenario analyses assessed the impact of uptake rates, seasonal severity and administration windows.Results Without intervention, a Swedish birth cohort (98,475 infants in 2024) was projected to experience 1,452 RSV hospitalisations, 7,841 outpatient visits, and 1 RSV death, costing SEK 252.3 million. Maternal RSVpreF vaccination alone reduced RSV hospitalisations by 33.3% and outpatient visits by 22.0%, yielding net savings of SEK 19.4 million (total SEK 232.9 million) and +18 QALYs (dominant, i.e. more effective and less costly). Nirsevimab alone reduced RSV hospitalisations by 35.7% and outpatient visits by 32.3%, but increased costs to SEK 302.3 million (ICER SEK 1,328,063/QALY). The complementary strategy reduced RSV hospitalisations by 40.8% and outpatient visits by 28.5% and was cost-saving (SEK 243.8 million; dominant).Conclusion Compared with no intervention, all three strategies reduced RSV-related morbidity in Swedish infants. Maternal RSVpreF vaccination alone was the most economically favourable option, while the complementary strategy, including both maternal RSVpreF vaccination and nirsevimab, achieved the largest health gains and was also dominant. Nirsevimab alone reduced RSV burden but at substantially higher incremental cost per QALY.