Tab. II.

Real-world effectiveness data with a single dose of Nirsevimab.

Country	Study Details	Population	Main Results	Strengths
Luxembourg	Ernst et al. 2024 [36] Paediatric RSV-H in children ≤ 5 years	Infants born between Oct. 1, 2023, and Mar. 31, 2024: N = 1524 4 hospitals, the entire country	nIC coverage with Nirsevimab from Oct to mid-Dec.: 1277/1524 (84%) Reduction in RSV-H: children ≤ 5 years -38%, infants < 6 months -69% Reduction in the proportion of hospitalised children < 5 years in PICUs: 2022: 36/389 (9.3%), 2023: 15/241 (6.2%) Increase in the average age of children hospitalised in 2023: 7.8 months in 2022, 14.4 months in 2023	First real-world data on the effectiveness of Nirsevimab in protecting infants from severe RSV disease
Spain	Lopez-Lacort et al. 2024 [38] Paediatric RSV-LRTI-H in infants < 9 months	Infants during their first RSV season (born on or after Apr. 1, 2023) N = 15676 9 hospitals, 3 regions (Valencia, Murcia, Valladolid)	nIC with Nirsevimab ranges from 78.7% to 98.6% Effectiveness in preventing RSV-LRTI-H in infants < 9 months: 70.2% (95% CI: 38.3-88.5) Valencia: 69.3% (95% CI: 36.4-86.2), Murcia: 86.9% (95% CI: 77.1-92.9), Valladolid: 97.0% (95% CI: 87.7-99.6) Effectiveness in preventing LRTI-negative RSV admissions: 32.4% (95% CI: -27.5-63.4). Reduction in RSV-H in infants: 70.2% (95% CI: 38.3-88.5)	Uniform methodology to detect hospitalised RSV cases in three Spanish regions Simultaneous use of screening approach and test-negative design Active surveillance of respiratory infections in all nine hospitals
	Ezpeleta et al. 2024 [39] Paediatric RSV-H in children born in Navarra	Infants born between Oct. 2023 and Jan. 2024 N = 1771 All hospitals, 1 region (Navarra)	nIC with Nirsevimab from Oct 2023 to Jan.2024: 1083/1771 (92%) Effectiveness in preventing RSV-H in infants: 88.7% (95% CI: 69.6-95.8) Reduction in the risk of RSV-H: Immunised 8/1083 (0.7%), Non-immunised 8/94 (8.5%) Reduction in the risk of RSV-ICU admission: Immunised 3/1083 (0.3%), Non-immunised 2/94 (2.1%) Vaccination of infants born from Sep. 2023 to Jan. 2024 prevents one hospitalisation per 15.3 immunized infants and avoids 77.5% (95.4/121.5) of the hospitalisations	Effectiveness and impact of the prospective immunisation strategy against RSV-H Provides a benchmark to compare the effectiveness of different immunisation strategies against RSV
	Martinón-Torres et al. 2023 [37] Mallah et al. 2024 [40] Ares-Gómez et al. 2024 [41] Paediatric RSV-LRTI-H in children Very severe RSV-LRTI ICU admissions LRTI admission for all causes	Infants born between Sep. 25, 2023, and Mar. 31, 2024 N = 10259 14 hospitals, 1 region (Galicia)	nIC with Nirsevimab ranges from 81.4% to 97.5% Effectiveness in preventing RSV-LRTI-H in infants: 82.0% (95% CI 65.6-90.2%) Reduction in the risk of RSV-LRTI-H: Immunised 30/9408 (0.3%), Non-immunised 16/851 (1.9%) Effectiveness in preventing RSV-LRTI-H in ICU: 86.9% (95% CI 69.1-94.2%) Reduction in the risk of RSV-LRTI ICU admission: Immunised 15/9408 (0.16%), Non-immunised 10/851 (1.18%) Average RSV-LRTI-H prevented per 1000 infants: 407 (Effectiveness: 89.84%)	Rapid and effective implementation of Nirsevimab in the Galician neonatal population A robust information and education campaign and a flexible booking system facilitated high adherence Demonstration of Nirsevimab’s effectiveness in preventing RSV-LRTI-H and hospitalisations for all causes, consistent with previous clinical and real-world studies [28, 34, 38]
	Coma et al. 2024 [42] Effectiveness against: RSV infection Primary care attended bronchiolitis Viral Pneumonia Hospital Emergency Visit Hospital admission ICU admission	Infants born between Apr. and Sep. 2023 N = 26525 All hospitals, 1 region (Catalonia)	nIC with Nirsevimab: 23127/26525 (87.2%) Reduction in the risk of RSV-related hospital and ICU admissions: Hospital admission: 87.6% (95% CI: 82.1-91.4%) ICU admission: 90.1% (95% CI: 76.3-95.9%) Reduction in the risk of: RSV Infection: 68.9% (95% CI: 51.7-80%) Primary care attended bronchiolitis: 48.1% (95% CI: 42.4-53.3%) Viral Pneumonia: 60.7% (95% CI: 24.2-79.7%) Hospital Emergency Visit: 55.4% (95% CI: 48.4-61.5%)	Use of an integrated database allowing comprehensive analysis of the impact of the Catalan immunisation program on the reduction of RSV-related outcomes The analysis included a wide range of outcomes, offering a comprehensive evaluation of the efficacy of Nirsevimab across different levels of healthcare
United States	Moline et. Al 2024 [43] RSV-H among infants in their first RSV season	Infants born after Oct. 1, 2023, or aged less than 8 months on Oct. 1, 2023, N = 699 7 paediatric academic medical centres (Missouri, Ohio, New York, Washington, Texas, Pennsylvania, Tennessee)	nIC with Nirsevimab: High- Risk conditions 46% (18/39), No risk conditions 6% (41/660) Reduction in RSV-H: 90% (95% CI: 75-96%) Time elapsed between Nirsevimab administration and onset of ARI symptoms: 7-127 days; Median= 45 days (IQR = 19-76 days)	Inclusion of infants according to a standardised definition of ARI, ensuring uniformity of inclusion criteria Systematic testing for the presence of RSV reduces the risk of misdiagnosis or missed diagnosis
France	Paireau et al. 2024 [44] RSV bronchiolitis hospitalised in ICU from Sep. 15, 2023, to Jan. 31, 2024 (TND)	Infants (0-8 months) admitted to ICU in the period Sep. 15, 2023, to Jan. 31, 2024 N = 288 20 PICUs, metropolitan areas of the entire country	nIC with Nirsevimab: 58/288 (20.1%) Effectiveness in preventing severe RSV bronchiolitis in neonates admitted to the PICU: 75.9% (95%CI 48.5-88.7%)	Use TND to quickly estimate effectiveness based on surveillance data, reducing confounding bias and providing meaningful results
Italy	Consolati et. Al 2024 [45] RSV-H among infants in their first RSV season 2023-2024	Infants born between May 1, 2023, and Feb. 15, 2024, N = 537 1 hospital, 1 region (Valle d’Aosta)	nIC with Nirsevimab: in RSV season 77/89 (86%), out of RSV season 292/448 (65%) Reduction in hospitalisation cases for RSV bronchiolitis: -54% (47 cases in 2022-2023 season vs 18 cases in 2023-2024) Hospitalisations for bronchiolitis during the RSV season 2023-2024 after Nirsevimab introduction: Treated with Nirsevimab 0/369 (0%), No Prophylaxis 14/168 (8.3%)	Demonstration of the effectiveness and safety of universal prophylaxis with Nirsevimab in infants, with a marked reduction in the risk of RSV-H
RSV-H: RSV-related hospitalisation; RSV-LRTI-H: RSV-LRTI paediatric hospitalisation; nIC: neonatal immunisation coverage.