Respiratory Syncytial Virus (RSV) is one of the leading causes of lower respiratory tract infections and can lead to bronchiolitis and pneumonia in children under the age of five—particularly during the first year of life.

In Italy, RSV poses a significant challenge for the national healthcare system. During the 2022–2023 season, over 50% of influenza-like illnesses (ILIs) in children under the age of two were caused by RSV.

Data indicate that the virus was responsible for 73.5% of hospitalizations due to bronchiolitis, a condition that led to an increased demand for hospital beds to accommodate the rising number of admissions. In response to this threat, a new long-acting monoclonal antibody—Nirsevimab—has been developed to protect infants during their first season of RSV exposure.

How Does Nirsevimab Work?

Nirsevimab provides fast and effective protection in newborns. Unlike traditional vaccines, it acts directly after administration and does not require activation of the infant’s immune system. Delivered as a single dose via a pre-filled syringe, the antibody significantly reduces the risk of infection and serious complications.

Impact of Nirsevimab in Italy and Worldwide

In Italy, the Aosta Valley led the way in introducing Nirsevimab during the 2023–2024 season. The region launched a universal RSV prevention program, offering the antibody to all infants in their first year of life.

The results were encouraging: 71.5% of infants received immunization, and no cases of hospitalization for severe RSV-related respiratory infections were reported among them. In contrast, among non-immunized infants, the hospitalization rate reached 9.7%.

At the international level, the effectiveness of Nirsevimab has also been confirmed. In France, a 56% reduction in bronchiolitis cases was observed in children under 3 months of age, and a 28.1% decrease in older infants.

In Spain, regions such as Catalonia and Galicia also reported promising outcomes, with a significant reduction in hospitalizations and severe RSV cases.

With the rollout of broader immunization programs—such as the one implemented in the Aosta Valley—and the confirmation of its effectiveness across Europe, this monoclonal antibody is emerging as a promising solution to reduce the healthcare burden associated with RSV.

References

1. Sanofi e Sanità Pubblica: prevenzione RSV bambini. (s.d.). Missioneprevenzione: il portale per la prevenzione. https://www.missioneprevenzione.it/su-di-noi/notizie/sanofi-al-fianco-della-sanità-pubblica-per-un-cambio-di-paradigma-nella-prevenzione-del-virus-respiratorio-sinciziale-rsv-in-tutti-i-bambini-nel-primo-anno-di-vita
2. Profilassi contro RSV con anticorpo monoclonale: i dati italiani presentati all’ESPID – Quotidiano Sanità. (s.d.). QS – Quotidiano Sanità. https://www.quotidianosanita.it/scienza-e-farmaci/articolo.php?articolo_id=122455
3. Nirsevimab per la prevenzione delle infezioni da VRS (Virus Respiratorio Sinciziale) nel neonato: ok dal Board del Calendario Vaccinale per la Vita e dalla Società Italiana di Neonatologia – Vaccinarsi in Puglia. (s.d.). Vaccinarsi in Puglia: Informarsi sulle vaccinazioni. https://vaccinarsinpuglia.org/notizie/2023/03/nirsevimab-per-la-prevenzione-delle-infezioni-da-vrs-(virus-respiratorio-sinciziale)-nel-neonato-ok-dal-board-del-calendario-vaccinale-per-la-vita-e-dalla-società-italiana-di-neonatologia