Modelling the potential clinical and economic impact of universal immunisation with nirsevimab versus standard of practice for protecting all neonates and infants in their first respiratory syncytial virus season in Spain

Abstract

Background: Respiratory syncytial virus (RSV) is associated with substantial morbidity among infants. This study modelled the potential public health and economic impact of nirsevimab, a long-acting monoclonal antibody, as an immunoprophylactic strategy for all infants in Spain in their first RSV season.

Methods: A static decision-analytic model of the Spanish birth cohort during its first RSV season was developed to estimate the impact of nirsevimab on RSV-related health events and costs versus the standard of practice (SoP). Spain-specific costs and epidemiological data were used as model inputs. Modelled outcomes included RSV-related outpatient visits, emerging room (ER) visits, hospitalisations - including pediatric intensive care unit (PICU) admission, mechanical ventilation, and inpatient mortality.

Results: Under the current SoP, RSV caused 151,741 primary care visits, 38,798 ER visits, 12,889 hospitalisations, 1,412 PICU admissions, and 16 deaths over a single season, representing a cost of €71.8 million from a healthcare payer perspective. Universal immunisation of all infants with nirsevimab was expected to prevent 97,157 primary care visits (64.0% reduction), 24,789 ER visits (63.9%), 8,185 hospitalisations (63.5%), 869 PICU admissions (61.5%), and 9 inpatient deaths (52.6%), saving €47.8 million (62.4%) in healthcare costs.

Conclusions: These results suggest that immunisation with nirsevimab of all infants experiencing their first RSV season in Spain is likely to prevent thousands of RSV-related health events and save considerable costs versus the current SoP.

Keywords: Hospitalisation; Immunisation; Infant; Nirsevimab; Public health; Respiratory syncytial viruses; Respiratory tract infections; Spain.

Fig. 1

Model structure. Abbreviations ER, emergency room; PICU, pediatric intensive care unit

Fig. 2

Immunisation strategies. Standard of practice (SoP) in Spain is to administer palivizumab monthly, for up to 5 doses, to eligible infants during their first respiratory syncytial virus (RSV) season (November to March; left panel) [32] and to provide supportive care for preterm and term infants not eligible for palivizumab. A strategy using a single dose of nirsevimab for all infants during their first RSV season was investigated (right panel). Shaded months indicate protection from RSV from immunisation with palivizumab or nirsevimab. A 5-month duration of protection from a single nirsevimab injection was assumed based on the duration of protection evaluated in the pivotal study [18]

Fig. 3

Current RSV burden over the first RSV season. Hospitalisation costs include PICU and MV cases. Numbers are rounded to the nearest digit. Abbreviations ER, emergency room; MV, mechanical ventilation; PICU, pediatric intensive care unit; RSV, respiratory syncytial virus

Fig. 4

Modelled RSV burden in infants born within and outside of the RSV season. Burden shown under two scenarios: all infants immunised during RSV season with nirsevimab and high-risk infants immunised according to SoP. Hospitalisations include intensive care unit and mechanical ventilation cases. Nirsevimab describes strategy 2 (single dose of nirsevimab for all infants). SoP describes strategy 1 (palivizumab only for palivizumab subpopulation and no prophylaxis for the rest). Numbers are rounded to the nearest digit. Abbreviations: RSV, respiratory syncytial virus; SoP, standard of practice

Fig. 5

Modelled impact of nirsevimab immunisation. Hospitalisations include intensive care unit and mechanical ventilation cases. Numbers are rounded to the nearest digit. Abbreviation PICU, pediatric intensive care unit

Fig. 6

Scenario analysis results – health events averted. Low efficacy estimate = 65.9% nirsevimab efficacy (1st dose) among preterm and term infants. High efficacy estimate = 87.7% nirsevimab efficacy (1st dose) among preterm and term. RSV Specific definition = Monthly probability of RSV infections 0.33–29.94%; specialist visits: 0.02-0.97%; ER visits: 0.44–21.21%; GP visits: 0.96–81.1%. Mortality scenario 1 = 0.53% inpatient mortality among palivizumab-eligible and preterm infants [47]; mortality scenario 2 = 2.33% inpatient mortality among palivizumab-eligible and preterm infants [15]; mortality scenario 3 = 1.00% inpatient mortality in palivizumab-eligible infants and 0.80% inpatient mortality in other preterm infants [30]; mortality scenario 4 = 0.15% inpatient mortality among term infants [48]. Numbers are rounded to the nearest digit. Abbreviations: ER, emergency room; RSV, respiratory syncytial virus

Fig. 7

Deterministic sensitivity analysis. Tornado plot shows healthcare costs averted