Respiratory syncytial virus-related lower respiratory tract infection hospitalizations in infants receiving nirsevimab in Galicia (Spain): the NIRSE-GAL study

Eur J Pediatr. 2025 May 2;184(5):321. doi: 10.1007/s00431-025-06151-3.

Abstract

As part of the NIRSEGAL study ( https://www.nirsegal.es/en ), we present the clinical characteristics and course of respiratory syncytial virus (RSV)-related low respiratory tract infection (LRTI) hospitalizations in infants eligible for nirsevimab administration during the 2023-2024 season. Infants eligible for nirsevimab immunization (born between 1 April, 2023, and 30 March, 2024) who were hospitalized due to RSV-related LRTI between September 25, 2023, and April 15, 2024, in a hospital from the Galician Public Health system were included. Clinical and demographic characteristics of RSV-related LRTI hospitalizations were analyzed, with comparisons made between breakthrough cases (those immunized with nirsevimab) and non-breakthrough cases. During the study period, 69 RSV-related LRTI hospitalizations were recorded, with a median hospital stay of 4 (interquartile range (IQR) 3-6) days; 65.2% (N = 45) were breakthrough cases. The median age was 2.7 (IQR 1.5-5.2) months, and more than half of them (N = 39, 56.5%) were male. The incidence of cases was parallel to the RSV epidemic curve, suggesting no waning of nirsevimab efficacy. Of the total hospitalizations, 16 infants (23.2%) had a high-risk condition, 44 (63.8%) needed oxygen support, 15 (21.7%) were admitted to the intensive care unit (ICU), and 11 (15.9%) received non-invasive mechanical ventilation (NIMV). No statistically significant differences were observed in these characteristics when comparing breakthrough and non-breakthrough cases.

Conclusion: In the nirsevimab era, a substantial proportion of children who were hospitalized for RSV-related LRTI needed oxygen support, NIMV, and ICU admission. Clinical characteristics, timing, and outcomes were comparable between breakthrough and non-breakthrough cases.

Trial registration: The NIRSE-GAL study protocol was registered on ClinicalTrials.gov (NCT06180993).

What is known: • Nirsevimab, a long-acting monoclonal antibody, has shown high effectiveness in preventing RSV-related hospitalizations and has been included in some European countries' immunization programs.

What is new: • During the first RSV season after the universal implementation of nirsevimab in Galicia (Spain), a large proportion of hospitalized infants had high-risk conditions, yet disease severity markers (oxygen need, ICU admission, NIVM) were comparable between breakthrough and non-breakthrough cases. • No signal of waning protection over time was observed among breakthrough cases, reinforcing the potential value of early, season-wide immunization.

Keywords: Breakthrough cases; Immunization; Infants; Low respiratory tract infection (LRTI); Nirsevimab; Respiratory syncytial virus (RSV).

Publication types

  • Multicenter Study
  • Observational Study

MeSH terms

  • Antibodies, Monoclonal, Humanized* / therapeutic use
  • Antiviral Agents* / therapeutic use
  • Female
  • Hospitalization* / statistics & numerical data
  • Humans
  • Infant
  • Male
  • Respiratory Syncytial Virus Infections* / drug therapy
  • Respiratory Syncytial Virus Infections* / epidemiology
  • Respiratory Syncytial Virus Infections* / therapy
  • Respiratory Tract Infections* / epidemiology
  • Respiratory Tract Infections* / therapy
  • Respiratory Tract Infections* / virology
  • Spain / epidemiology

Substances

  • Antibodies, Monoclonal, Humanized
  • Antiviral Agents

Associated data

  • ClinicalTrials.gov/NCT06180993