Real-world evidence

AE, adverse event; GA, gestational age; LRTI, lower respiratory tract disease; RSV, respiratory syncytial virus.
a. Immunisation campaign: September 25, 2023–March 31, 2024. Eligible infants in Galicia included those aged <6 months at the start of the immunisation campaign (born between April 1 and September 24, 2023 [catch-up group]) and those born during the immunisation campaign (born between September 25 2023 and March 31 2024 [seasonal group]. A high-risk group was also immunised (n=348/360) as part of the Galician immunisation campaign. This group was not included in effectiveness or public health impact calculations.¹
† Effectiveness and impact were estimated using the seasonal and catch-up groups. Nirsevimab effectiveness was estimated from incidence rate ratios calculated using Poisson regression models, which were adjusted for enrolment group (catch-up and seasonal), sex, and health district area. Only patients with non-zero follow-up time were included.¹ 
‡ Adverse events related to Beyfortus administration were routinely monitored through the Galician pharmacovigilance system. In addition, active surveillance of any potential adverse event or hospitalisation in the first 3 weeks after Beyfortus administration was conducted in the pre-term population (infants with a GA <37 weeks).² 
* IQR: 89.1–91.4%. **P-values were obtained from linear regression model analysis of weekly accumulated incidence rates comparing the 2023–2024.

1. Ares-Gómez S et al. Lancet Infect Dis 2024; 24(8): 817–824. 
2. Mallah N et al. Lancet Infect Dis 2024; 25(2): E62–E63 & Supplementary Appendix. 
3. Griffin MP et al. N Engl J Med 2020; 383(5): 415–425. 
4. Hammitt LL et al. N Engl J Med 2022; 386(9): 837–846. 
5. HSE press release. Available at https://about.hse.ie/news/new-hse-rsv-immunisation-programme-significantly-reduces-infections-serious-illness-and-hospitalisations-in-babies/. Last accessed May 2025.