- Article
- Source: Campus Sanofi
- 21 Nov 2025
Beyfortus▼ (Nirsevimab): Help protect the unprotected
RSV poses a risk for all infants2,3
Respiratory syncytial virus (RSV) is a common virus causing respiratory tract infections. While usually mild and self-limiting, RSV affects approximately 329,425 children under 5 years old each year in the UK, primarily between October and March. In infants, who are at an increased risk of LRTI, it carries a significant disease burden, with babies 0–12 months old incurring 49% of the total annual cost of RSV in children under 5 years in the UK, in addition to the emotional and practical burden on families and carers.2-4
All infants need protection from RSV infection.5,6 RSV infection is:
Common
Two out of three infants will be infected with RSV by the age of 17
Serious
Leading cause of infant hospitalisations and LRTI5
Infants are 14× more likely to be hospitalised due to RSV than the common flu8
Unpredictable
Among infants hospitalised for RSV:
~50% were born out of RSV season9
>70% were born at term and healthy6,10
Watch Dr Simon Nadel discuss the risk of RSV to all infants
Understanding the protection gaps in the UK
Regardless of gestational age, all preterm infants are at higher risk of RSV complications, including hospitalisation.11
A maternal immunisation programme was launched in 2024 in the UK, and from September 2025, the programme includes Beyfortus (nirsevimab) for very and extremely premature infants (born <32 wGA).2
In theory, this updated programme should offer comprehensive protection for all babies. But in practice, it may leave a substantial number of preterm infants (born between 32 and 36 wGA) unprotected for their first winter respiratory season.12
Besides this, thousands of healthy and at term infants remain vulnerable as they enter their first RSV season due to significant protection gaps in the current childhood RSV immunisation programme. Not all eligible mothers receive vaccination, the latest published report in April 2025 showed an uptake of 54%.13 In addition, for those who do receive the vaccine, there will continue to be babies who are unable to benefit:2,14,-16
- infants born too soon after maternal immunisation
- infants born more than 6 months before RSV season
- infants whose maternal antibodies will wane during the season
Dr Simon Nadel discusses RSV in unprotected infants
Impact on infants
Data from 21 NHS trusts during the 2024–2025 RSV season in England demonstrates that hospitalisation associated with RSV is still a burden on infants. Of the 2,149 RSV hospital admissions in children under 5 (excluding ICU and HDU admissions), 58.8% were infants aged under 1, with 879 aged 6 months and younger. In addition, a further 164 infants (<1 year) were admitted to intensive care and high dependency units, with 80% being below 6 months of age.17
RSV is a threat to all infants, yet many remain vulnerable without protection this season12,13,16
HDU: high dependency unit; ICU: intensive care unit; LRTI: lower respiratory tract infection; wGA: weeks of gestational age
- Beyfortus Summary of Product Characteristics.
- UK Health Security Agency. Respiratory syncytial virus (RSV): The Green Book, chapter 27a, 20 March 2013 (last updated 14 July 2025). Available at: gov.uk Accessed November 2025
- Fusco F, Hocking L et al. The burden of respiratory syncytial virus: understanding impacts on the NHS, society and economy. RAND Europe, Cambridge, UK, 2022. Available at: rand.org Accessed November 2025
- Kieffer A, Beuvelet M et al. Disease burden associated with all infants in their first RSV season in the UK: a static model of universal immunization with nirsevimab against RSV‑related outcomes. Infect Dis Ther 2024;13:2135‑2153
- Drysdale, S. B., Sande, C. J., Green, C. A., & Pollard, A. J. (2015). RSV vaccine use – the missing data. Expert Review of Vaccines, 15(2), 149–152. https://doi.org/10.1586/14760584.2016.1114419
- Hall C B, Weinberg G A et al. Respiratory syncytial virus‑associated hospitalizations among children less than 24 months of age. Pediatrics 2013;132:e341‑e348
- Glezen W P, Taber L H et al. Risk of primary infection and reinfection with respiratory syncytial virus. Am J Dis Child 1986;140:543‑546
- Schanzer D L, Saboui M et al. Burden of influenza, respiratory syncytial virus, and other respiratory viruses and the completeness of respiratory viral identification among respiratory inpatients, Canada, 2003‑2014. Influenza Other Respir Viruses 2018;12:113‑121
- Demont C, Petrica N et al. Economic and disease burden of RSV‑associated hospitalizations in young children in France, from 2010 through 2018. BMC Infect Dis 2021;21:730
- Arriola C S, Kim L et al. Estimated burden of community‑onset respiratory syncytial virus‑associated hospitalizations among children aged <2 years in the United States, 2014‑15. J Pediatric Infect Dis Soc 2020;9:587‑595
- Griffin M P, Yuan Y et al. Single‑dose nirsevimab for prevention of RSV in preterm infants. N Engl J Med 2020;383:415‑425
- Sanofi. Data on file. Beyfortus (nirsevimab) BIM for infants >=32 wGA 2025
- GOV.UK. Respiratory syncytial virus (RSV) maternal vaccination coverage in England: April 2025, updated 25 September 2025. Available at: gov.uk. Accessed November 2025
- Department of Health and Social Care. Respiratory syncytial virus (RSV) immunisation programme for infants and older adults: JCVI full statement, 11 September 2023. Available at: gov.uk. Accessed November 2025
- Abrysvo Summary of Product Characteristics. Available at: medicines.org. Accessed November 2025
- Williams T C, Marlow R et al. Bivalent prefusion F vaccination in pregnancy and respiratory syncytial virus hospitalisation in infants in the UK: results of a multicentre, test‑negative, case‑control study. Lancet Child Adolesc Health 2025;9:655‑662
- UK Health Security Agency. Surveillance of respiratory syncytial virus: winter 2024 to 2025, 31 July 2025. Available at: gov.uk. Accessed November 2025
MAT-XU-2504838 (v1.0) Date of preparation: December 2025