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. 2025 Dec;19(12):e70186.
doi: 10.1111/irv.70186.

Nirsevimab Effectiveness Against RSV-Related Hospitalisations in Children Under 24 Months: A Test-Negative Case-Control Study in Portugal, 2024-2025

Vânia Gaio  1   2 , Camila Henriques  3 , Miguel Lança  3   4 , Rita Marques  5 , Raquel Marques  5 , Marta Rodrigues  6 , Sofia Almeida  6 , Beatriz Sousa  7 , Margarida Freitas  7 , Diana Amaral  8 , Sara Ferreira  8 , Inês Azevedo  9 , Madalena von Hafe  9 , Rafaela Gonçalves  10 , Regina Viseu  10 , Teresa Bandeira  11 , Carolina Constant  11 , Madalena Malato  12 , Inês Carvalho  12 , Jorge Rodrigues  13 , Margarida Farinha  13 , Teresa Nunes  14 , Teresa Graça  14 , Sofia Gomez  15 , Sara Soares  15 , João Farela Neves  16 , Paulo Paixão  16 , Inês Piscalho  17 , Ana Loureiro  17 , Cristina Freitas  18 , José Alves  18 , Diana Soares  19 , Paulo Lopes  19 , Ausenda Machado  1   2 , Raquel Guiomar  3 , Ana Paula Rodrigues  1 ; VigiRSV Group
Collaborators, Affiliations

Nirsevimab Effectiveness Against RSV-Related Hospitalisations in Children Under 24 Months: A Test-Negative Case-Control Study in Portugal, 2024-2025

Vânia Gaio et al. Influenza Other Respir Viruses. 2025 Dec.

Abstract

We assessed Nirsevimab effectiveness (NE) against respiratory syncytial virus (RSV)-related hospitalisation in eligible children (< 2 years) using a test-negative case-control design within the VigiRSV network (weeks 43/2024 to 16/2025). Among 341 participants (median age: 2 months; 91.2% without known chronic condition), 137 (40.2%) tested RSV-positive. Adjusted NE against RSV-related hospitalisation was 78.5% (95%CI: 59.3-89.0). Sensitivity analyses confirmed the robustness of the results. These findings support Nirsevimab's effect in a predominantly healthy infant population and contribute to informing public health decisions for RSV immunisation.

Keywords: RSV‐related hospitalisations; children; effectiveness; nirsevimab.

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Conflict of interest statement

The authors declare no conflicts of interest.

Figures

FIGURE 1
FIGURE 1
Flow chart of participants selected for the study.
FIGURE 2
FIGURE 2
Distribution of cases and controls on the epidemic curve, considering the study period between Week 43/2024 and Week 16/2025.
See this image and copyright information in PMC

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