Clinical Profile of RSV Breakthrough Infections After Nirsevimab Introduction.
4 affiliations
- 1General Pediatric and Infectious Disease Unit, Pediatric Emergency Medicine, Bambino Gesù Children's Hospital, IRCCS, 00165 Rome, Italy.
- 2Neonatal Intensive Care Unit, Bambino Gesù Children's Hospital, IRCCS, 00165 Rome, Italy.
- 3Microbiology and Diagnostic Immunology Unit, Bambino Gesù Children's Hospital, IRCCS, 00165 Rome, Italy.
- 4Systems Medicine Departments, Tor Vergata University of Rome, 00133 Rome, Italy.
Abstract
The introduction of universal prophylaxis with nirsevimab for all children in their first epidemic season has substantially reduced the burden of respiratory syncytial virus (RSV). However, a small number of breakthrough infections continue to occur despite immunization, mostly in previously healthy infants, and these cases remain incompletely characterized. We conducted a retrospective study across three epidemic seasons at a third-level hospital, including 536 RSV-positive children under 12 months of age hospitalised for bronchiolitis. Immunised infants with breakthrough infection showed a higher prevalence of prematurity and comorbidities than unimmunised infants, and were more frequently represented in the 9-12-month age group, with a median of 291 days since nirsevimab administration. Immunised infants had significantly lower odds of requiring supplemental oxygen (aOR 0.33, 95% CI 0.19-0.57, p < 0.001). However, once oxygen therapy was required, immunisation status did not independently predict the need for advanced ventilatory support. Severe breakthrough cases requiring invasive mechanical ventilation occurred even among infants without traditional risk factors. These findings confirm the substantial real-world impact of universal nirsevimab prophylaxis while underscoring the need for continued clinical vigilance and further research into the mechanisms underlying breakthrough disease.
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BibTeX
@article{vittucci2026clinical,
title = {{Clinical Profile of RSV Breakthrough Infections After Nirsevimab Introduction.}},
author = {Anna Chiara Vittucci and Livia Antilici and Alessandra Salvatori and Domenico Umberto De Rose and Rossana Scutari and Velia Chiara Di Maio and Lelia Rotondi Aufiero and Mara Pisani and Anna Maria Musolino and Andrea Dotta and Carlo Federico Perno and Alberto Villani},
journal = {Viruses},
year = {2026},
month = oct,
doi = {10.3390/v18101107},
url = {https://europepmc.org/article/MED/42944027},
note = {CC BY},
}
RIS
TY - JOUR
TI - Clinical Profile of RSV Breakthrough Infections After Nirsevimab Introduction.
AU - Anna Chiara Vittucci
AU - Livia Antilici
AU - Alessandra Salvatori
AU - Domenico Umberto De Rose
AU - Rossana Scutari
AU - Velia Chiara Di Maio
AU - Lelia Rotondi Aufiero
AU - Mara Pisani
AU - Anna Maria Musolino
AU - Andrea Dotta
AU - Carlo Federico Perno
AU - Alberto Villani
PY - 2026
DA - 2026/10/07
JO - Viruses
DO - 10.3390/v18101107
UR - https://europepmc.org/article/MED/42944027
AB - The introduction of universal prophylaxis with nirsevimab for all children in their first epidemic season has substantially reduced the burden of respiratory syncytial virus (RSV). However, a small number of breakthrough infections continue to occur despite immunization, mostly in previously healthy infants, and these cases remain incompletely characterized. We conducted a retrospective study across three epidemic seasons at a third-level hospital, including 536 RSV-positive children under 12 months of age hospitalised for bronchiolitis. Immunised infants with breakthrough infection showed a higher prevalence of prematurity and comorbidities than unimmunised infants, and were more frequently represented in the 9-12-month age group, with a median of 291 days since nirsevimab administration. Immunised infants had significantly lower odds of requiring supplemental oxygen (aOR 0.33, 95% CI 0.19-0.57, p < 0.001). However, once oxygen therapy was required, immunisation status did not independently predict the need for advanced ventilatory support. Severe breakthrough cases requiring invasive mechanical ventilation occurred even among infants without traditional risk factors. These findings confirm the substantial real-world impact of universal nirsevimab prophylaxis while underscoring the need for continued clinical vigilance and further research into the mechanisms underlying breakthrough disease.
SN - 1999-4915
ER -