What is the clinical evidence from this study?

Study design: Case Report. Population: RSV-B infection (n=3). Intervention: RSV-B F:N201T substitution. Primary outcome: Hospitalization and nirsevimab recognition.

What does this research mean for the field?

RSV-B variants carrying the F protein N201T substitution exhibit reduced susceptibility to nirsevimab and are emerging sporadically across distinct viral backgrounds, causing severe infections in immunized children. Novelty: ClaimNovelty.NOVEL_FINDING. Consensus alignment: ConsensusAlignment.NEUTRAL.

What question did this study set out to answer?

To identify and characterize RSV-B variants carrying the F:N201T substitution associated with breakthrough infections following nirsevimab administration.

September 6, 2026EurosurveillanceOpen Access

Detection of nirsevimab-resistant RSV-B variants in children carrying the F:N201T substitution through genomic surveillance, Spain, 2025/26 season

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Population

Three children infected with RSV-B viruses carrying the F protein N201T substitution in Spain

Design

Genomic surveillance and recombinant expression study

Key result

Three children infected with RSV-B carrying the F:N201T substitution showed reduced nirsevimab recognition, with two requiring hospitalization despite receiving nirsevimab that season.

Authors

MIMaría Iglesias‐Caballero JIJosé Alfonso Apesteguía Infantes ACAlbert Campoy

Discussion

Member takes

Overview

Nirsevimab-treated children with RSV-B breakthroughs may harbor F:N201T variants; case data leave open population-level implications for monoclonal prophylaxis.

Key Points

To identify and characterize RSV-B variants carrying the F:N201T substitution associated with breakthrough infections following nirsevimab administration.
Conducted genomic surveillance on pediatric RSV-B infections during the 2025/26 season in Spain (N=3 cases).
Evaluated clinical severity in three children exposed to nirsevimab.
Performed recombinant protein expression assays and phylogenetic analyses to assess antibody binding and evolutionary lineage patterns.
Identified the F:N201T mutation in three children, leading to hospitalization in two recently treated patients (one requiring intensive care).
Recombinant expression assays confirmed reduced nirsevimab recognition against the N201T mutant protein.
Genomic analyses indicated sporadic independent emergence across diverse RSV-B backgrounds rather than clonal spread of a single lineage.

Study Design

Type

Case Report (n=3)

Structured PICO

Population

3 children infected with RSV-B viruses carrying the F protein N201T substitution during the 2025/26 season in Spain.

Exposure

Nirsevimab

Outcome

Detection of nirsevimab-resistant RSV-B variants and clinical outcomes (hospitalization)

Genomic surveillance identified sporadic emergence of RSV-B variants with the F:N201T substitution that confer reduced susceptibility to nirsevimab in children.

Cite This Study

Iglesias‐Caballero et al. (2026) conducted a case report in RSV-B infection (n=3). RSV-B F:N201T substitution was evaluated on Hospitalization and nirsevimab recognition. Three children infected with RSV-B carrying the F:N201T substitution showed reduced nirsevimab recognition, with two requiring hospitalization despite receiving nirsevimab that season.

synapsesocial.com/papers/6a9d1eb628139818eab21c4d https://doi.org/10.2807/1560-7917.es.2026.31.35.2600690

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September 6, 2026EurosurveillanceOpen Access

Detection of nirsevimab-resistant RSV-B variants in children carrying the F:N201T substitution through genomic surveillance, Spain, 2025/26 season

View Full Paper

Ask AI

Bookmark

Population

Three children infected with RSV-B viruses carrying the F protein N201T substitution in Spain

Design

Genomic surveillance and recombinant expression study

Key result

Three children infected with RSV-B carrying the F:N201T substitution showed reduced nirsevimab recognition, with two requiring hospitalization despite receiving nirsevimab that season.

Authors

MIMaría Iglesias‐Caballero JIJosé Alfonso Apesteguía Infantes ACAlbert Campoy

Discussion

Member takes

Overview

Nirsevimab-treated children with RSV-B breakthroughs may harbor F:N201T variants; case data leave open population-level implications for monoclonal prophylaxis.

Key Points

To identify and characterize RSV-B variants carrying the F:N201T substitution associated with breakthrough infections following nirsevimab administration.
Conducted genomic surveillance on pediatric RSV-B infections during the 2025/26 season in Spain (N=3 cases).
Evaluated clinical severity in three children exposed to nirsevimab.
Performed recombinant protein expression assays and phylogenetic analyses to assess antibody binding and evolutionary lineage patterns.
Identified the F:N201T mutation in three children, leading to hospitalization in two recently treated patients (one requiring intensive care).
Recombinant expression assays confirmed reduced nirsevimab recognition against the N201T mutant protein.
Genomic analyses indicated sporadic independent emergence across diverse RSV-B backgrounds rather than clonal spread of a single lineage.

Study Design

Type

Case Report (n=3)

Structured PICO

Population

3 children infected with RSV-B viruses carrying the F protein N201T substitution during the 2025/26 season in Spain.

Exposure

Nirsevimab

Outcome

Detection of nirsevimab-resistant RSV-B variants and clinical outcomes (hospitalization)

Genomic surveillance identified sporadic emergence of RSV-B variants with the F:N201T substitution that confer reduced susceptibility to nirsevimab in children.

Cite This Study

synapsesocial.com/papers/6a9d1eb628139818eab21c4d https://doi.org/10.2807/1560-7917.es.2026.31.35.2600690

View Full Paper

Ask AI

Bookmark