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2025 theme: Vaccines

Abstract

BACKGROUND

In autumn 2023, Spain recommended nirsevimab to all infants born after 1 April 2023, as catch-up or at-birth immunisation.

AIM

We estimated effectiveness of a single nirsevimab dose against respiratory syncytial virus (RSV) hospitalisations throughout two seasons in healthy term-born infants.

METHODS

Cases were children born 1 April 2023 through 31 March 2024 after 35 gestation weeks without major comorbidities and hospitalised for RSV infection between 2023 immunisation campaign onset and 31 March 2025. We selected four healthy population-density controls per case, matched by province and birth date. Using target trial emulation, causal per-protocol effectiveness was estimated for catch-up (within 30 days of 2023 campaign onset) and at-birth immunisation (within 14 days of life) through cloning, censoring and inverse-probability-weighted conditional logistic regression.

RESULTS

We included 235/905 cases/controls for catch-up and 334/1,292 cases/controls for at-birth immunisation (first season), and 188/713 cases/controls for catch-up and 328/1,269 cases/controls for at-birth immunisation (second season). Two-season effectiveness was 64% (95% confidence interval (CI): 52–72) and 67% (95% CI: 59–74) for catch-up and at-birth immunisation, respectively, compared with 78% (95% CI: 70–84) and 84% (95% CI: 79–88) during first season and −8% (95% CI: −88 to 38) and 20% (95% CI: −21 to 46) during second season.

CONCLUSION

Nirsevimab was an effective long-term population-level intervention, decreasing RSV hospitalisations by two-thirds during the first two seasons of life. Effectiveness during second season was low or null, although it may be underestimated due to unavoidable survivor bias. The RSV hospitalisation rate among immunised children did not rebound in the second season.

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Two-season effectiveness of a single nirsevimab dose against RSV hospitalisation in healthy term-born infants: a population-based case–control study, Spain, October 2023 to March 2025
<p class="citation"> <span>Citation style for this article:</span> <span class="meta-value authors"> <a href="/search?value1=Olivier+N%C3%BA%C3%B1ez&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Núñez Olivier</a>, <a href="/search?value1=Juan+Juaneda&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Juaneda Juan</a>, <a href="/search?value1=Montserrat+Martinez-Marcos&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Martinez-Marcos Montserrat</a>, <a href="/search?value1=Enriqueta+Mu%C3%B1oz+Plat%C3%B3n&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Muñoz Platón Enriqueta</a>, <a href="/search?value1=Eva+Rivas+Wagner&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Rivas Wagner Eva</a>, <a href="/search?value1=Mar%C3%ADa-Isolina+Santiago-P%C3%A9rez&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Santiago-Pérez María-Isolina</a>, <a href="/search?value1=Virginia+%C3%81lvarez+R%C3%ADo&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Álvarez Río Virginia</a>, <a href="/search?value1=Matilde+Zornoza+Moreno&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Zornoza Moreno Matilde</a>, <a href="/search?value1=Ana+Fern%C3%A1ndez+Ib%C3%A1%C3%B1ez&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Fernández Ibáñez Ana</a>, <a href="/search?value1=Gisselle+Perez+Suarez&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Perez Suarez Gisselle</a>, <a href="/search?value1=Gorka+Loro%C3%B1o+Ortiz&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Loroño Ortiz Gorka</a>, <a href="/search?value1=Nerea+Eg%C3%BC%C3%A9s&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Egüés Nerea</a>, <a href="/search?value1=Bel%C3%A9n+Berradre+S%C3%A1enz&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Berradre Sáenz Belén</a>, <a href="/search?value1=Mar%C3%ADa+de+los+%C3%81ngeles+Cuesta+Franco&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Cuesta Franco María de los Ángeles</a>, <a href="/search?value1=Susana+Casado+Cobo&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Casado Cobo Susana</a>, <a href="/search?value1=Mar%C3%ADa+Dom%C3%ADnguez+Padilla&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Domínguez Padilla María</a>, <a href="/search?value1=Daniel+Castrillejo&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Castrillejo Daniel</a>, <a href="/search?value1=Ana+M%C3%ADguez+Santiy%C3%A1n&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Míguez Santiyán Ana</a>, <a href="/search?value1=Luca+Basile&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Basile Luca</a>, <a href="/search?value1=Mar%C3%ADa+%C3%81ngeles+Rafael+de+la+Cruz+L%C3%B3pez&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Rafael de la Cruz López María Ángeles</a>, <a href="/search?value1=Diana+Sanabria+Curbelo&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Sanabria Curbelo Diana</a>, <a href="/search?value1=Olaia+P%C3%A9rez-Mart%C3%ADnez&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Pérez-Martínez Olaia</a>, <a href="/search?value1=M+Jes%C3%BAs+Rodr%C3%ADguez+Recio&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Rodríguez Recio M Jesús</a>, <a href="/search?value1=Lourdes+Duro+G%C3%B3mez&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Duro Gómez Lourdes</a>, <a href="/search?value1=Mar%C3%ADa+del+Pilar+Alonso+Vigil&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Alonso Vigil María del Pilar</a>, <a href="/search?value1=Manuel+Mendez+Diaz&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Mendez Diaz Manuel</a>, <a href="/search?value1=Rosa+Sancho&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Sancho Rosa</a>, <a href="/search?value1=Jes%C3%BAs+Castilla&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Castilla Jesús</a>, <a href="/search?value1=Ana+Carmen+Ib%C3%A1%C3%B1ez+P%C3%A9rez&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Ibáñez Pérez Ana Carmen</a>, <a href="/search?value1=Noa+Batalla+Rebollo&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Batalla Rebollo Noa</a>, <a href="/search?value1=Luc%C3%ADa+S%C3%A1nchez+Piorno&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Sánchez Piorno Lucía</a>, <a href="/search?value1=Ninoska+L%C3%B3pez+Berrios&option1=author&noRedirect=true" class="nonDisambigAuthorLink">López Berrios Ninoska</a>, <a href="/search?value1=Joaqu%C3%ADn+Lamas&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Lamas Joaquín</a>, <a href="/search?value1=Carmen+Olmedo&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Olmedo Carmen</a>, <a href="/search?value1=Susana+Monge&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Monge Susana</a>, <a href="/search?value1=Roberto+Pastor-Barriuso&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Pastor-Barriuso Roberto</a>, <a href="/search?value1=the+Nirsevimab+Effectiveness+Study+Collaborators&option1=author&noRedirect=true" class="nonDisambigAuthorLink">the Nirsevimab Effectiveness Study Collaborators</a></span>. Two-season effectiveness of a single nirsevimab dose against RSV hospitalisation in healthy term-born infants: a population-based case–control study, Spain, October 2023 to March 2025. <a href="/content/ecdc">Euro Surveill.</a> 2026;31(9):pii=2500593. <a href="https://doi.org/10.2807/1560-7917.ES.2026.31.9.2500593" title="doi link" target="_blank">https://doi.org/10.2807/1560-7917.ES.2026.31.9.2500593</a> <span class="ES_Article_citation"> <span class="generated">Received</span>: 06 Aug 2025;&nbsp;&nbsp; <span class="generated">Accepted</span>: 31 Oct 2025 </span> </p>
/content/10.2807/1560-7917.ES.2026.31.9.2500593
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