4CPS-187 Immunisation with nirsevimab: impact on RSV season in a paediatric hospital

<h3>Background and Importance</h3> Respiratory syncytial virus (RSV) is the leading cause of acute lower respiratory tract infections in children, having a considerable impact on healthcare system and later comorbidities. <h3>Aim and Objectives</h3> To describe the characteristics of patients admitted for RSV bronchiolitis during the first immunisation campaign with nirsevimab, conducted from October 2023 to March 2024 <h3>Material and Methods</h3> Prospective observational study. It included patients admitted for RSV infection who were eligible for nirsevimab. Campaign included infants under 6 months at the start, those born during the campaign and high-risk patients aged 6 months to 2 years. Collected variables: age, immunisation status, admission in Intensive Care Unit (ICU), suspected bacterial superinfection, type of respiratory support required, length of hospital stay (LOS) and oxygen therapy. <h3>Results</h3> Patients ≤ 6 months: There was a 67% reduction in admissions comparing the previous year (57 vs.172). Of the 57 admitted patients, 81% had not received immunisation and 10 patients were considered high-risk for severe disease, seven of whom were not immunised. All non-immunised patients (NIP) required respiratory support while 10% of immunised patients (IP) did not require it. Maximum respiratory support required is shown in table 1. Seventeen patients required ICU admission (76% NIP), with median ICU LOS of 3 (1–4) days, and 26% showed signs of bacterial superinfection. Median LOS for IP and NIP was 5 days with different ranges (2–12) for NIP and (3–7) for IP. <h3>Patients 6 months-2 years</h3> Ninety-nine percent of admitted patients were NIP (83), only 7% met immunisation criteria. Maximum respiratory support required is shown in table 2. Fifteen percent of the patients required ICU admission, with a median LOS of 4 (1–13) days, and the majority (10) had suspected bacterial superinfection. Sixty percent of the patients admitted to the ICU presented high-risk for severe disease. Median LOS was 4 days (1–37). <h3>Conclusion and Relevance</h3> In this study we appreciate a decrease in admissions among immunised patients; however, it does not seem to modify the course of the disease compared to non-immunised patients in terms of oxygen therapy needs and LOS, although there is a tendency to shorten them. Further studies are needed to confirm these observations. <h3>References and/or Acknowledgements</h3> <h3>Conflict of Interest</h3> No conflict of interest