RSV Immunisation in Infants: Why Real-World Evidence Matters

Respiratory Syncytial Virus (RSV) is a common respiratory infection that affects both infants and older adults. Almost every child encounters RSV within the first two years of life (RIVM, z.d.-b). In many cases, symptoms remain mild, such as a runny nose or cough. In others, RSV can lead to breathing difficulties and hospitalisation.

The burden is highest among infants and older adults with underlying conditions. In infants, most hospitalisations occur in those under six months (Respiratory Syncytial Virus (RSV) FAQs | NCIRS, 2026). RSV cases usually peak during the autumn and winter months, although in some years activity can extend into early spring. During these periods, RSV places clear pressure on healthcare systems, with increased admissions and demand for intensive care (RIVM, 2026). The impact also extends beyond hospitals. For example, parents often need to take time off from work to care of their children, which can create financial challenges for them, as well as wider societal costs (Franck et al., 2026).

In recent years, new immunisation therapies have become available after decades of limited progress (Principi et al., 2025). The two main approaches currently used are maternal vaccination, where pregnant women are vaccinated to pass protection to their newborns, and monoclonal antibodies, which are administered directly to infants. Both approaches have been shown to be effective in clinical trials and are now being actively implemented in national programmes.

These strategies are applied differently across countries. For example, Spain introduced monoclonal antibodies for newborns in 2023, right after the authorisation from the FDA and EMA. The UK followed in 2024 with a maternal vaccination programme. Most recently the Netherlands started its programme in 2025, using monoclonal antibodies. These choices are influenced by how countries evaluate disease burden, apply cost-effectiveness thresholds, and consider implementation feasibility.

The key questions now are: how do these strategies perform in real-world settings? And what is their impact on infants over time?

What Early Data Shows

Early observations from research suggest encouraging signals. In countries that have introduced immunisation programmes, reductions in hospital admissions among the youngest infants have been observed (Attaianese et al., 2025; Núñez et al., 2025).

At the same time, these findings are often based on short observation periods, typically covering a single season, and relatively small sample sizes confined to one country or even a specific region. This makes it difficult to draw robust conclusions or fully understand treatment effectiveness and long-term effects (Lee et al., 2025).

Reaching insights by comparing real-world data between hospitals and across countries over a long period of time is complex. The main challenges are:

1. The differences in rollout timing, uptake, and healthcare systems.
   Countries introduced immunisation programmes at different points in time and with different approaches. Uptake rates vary, and healthcare systems differ in how care is delivered and recorded.
2. Limited interoperability of data systems across countries and hospitals.
   Healthcare insights are often stored in different formats and systems that are not easily connected. This lack of interoperability limits the ease of comparing datasets across hospitals and countries.
3. Low patient volumes at hospital or regional level.
   At the level of a single hospital or region, the number of RSV cases can be too small to draw robust conclusions. This makes it challenging to identify clear patterns.

In addition, tracking patients over time to assess potential long‑term effects, often over several years, is extremely challenging.

The Role of Healthcare Observatories

To address these challenges, consistent and long-term, comparable data collection across hospitals and countries is necessary. Healthcare Observatories play a key role in enabling this. They provide a structured way to collect, harmonise, and analyse anonymised data across multiple hospitals, regions, and over time. By doing so, they help overcome data fragmentation within and between hospitals and support healthcare providers in making more informed decisions.

In the context of RSV, Healthcare Observatories can show:

• how hospitalisation rates among infants evolve following the introduction of an immunisation programme, both within and across countries
• how outcomes vary across different patient subgroups when stratified by characteristics, such as age, risk profiles, or underlying conditions
• how protection and outcomes develop over the longer term, across multiple RSV seasons
• how healthcare resource use and associated costs change over time

LOGEX has developed an Observatory in the field of Respiratory Tract Infections (RTI), which covers RSV, including data on prevention in infants. By combining insights across countries and over time, it provides a comprehensive view of RSV immunisationand its effects, helping clinicians, researchers, and policymakers better understand how different strategies perform in real-world settings and ultimately improve care.

Want to learn more about LOGEX RTI Observatory? Click here.

References

Attaianese, F., Trapani, S., Agostiniani, R., Ambrosino, N., Bertolucci, G., Biasci, P., Castelli, B., Colarusso, G., Coretti, G., Dani, C., Grosso, S., Lucenteforte, E., Maj, D., Martini, M., Mirri, G., Moriondo, M., Perone, V., Peroni, D., Rossetti, A., . . . Indolfi, G. (2025). Effectiveness of a targeted infant RSV immunization strategy (2024–2025): A multicenter matched case-control study in a high-surveillance setting. Journal Of Infection, 91(3), 106600. https://doi.org/10.1016/j.jinf.2025.106600

Franck, Z., Hofstraat, S., Jonker, L., Kragten, L., Messina, C., Fernandes, R. M., Bruijning-Verhagen, P., Farr, A., Hoste, L., Pana, Z. D., Smíšková, D., Hagstrøm, S., Jõgi, P., Nohynek, H. M., Frange, P., Delory, T., Pkhaladze, N., Rüdiger, M., Roilides, E., . . . Heath, P. (2026). The evolving landscape of RSV immunization: Current policies and practices across Europe. Vaccine, 76, 128222.

Lee, B., Trusinska, D., Ferdous, S., Pei, R., Kwok, H. H. Y., Schwarze, J., Williams, T. C., Gibbons, C., Quint, J. K., Sheikh, A., Drysdale, S. B., & Shi, T. (2025). Real-world effectiveness and safety of nirsevimab, RSV maternal vaccine and RSV vaccines for older adults: a living systematic review and meta-analysis. Thorax, 80(11), 838–848. https://doi.org/10.1136/thorax-2025-223376

Núñez, O., Olmedo, C., Moreno-Perez, D., Lorusso, N., Martínez, S. F., Villalba, P. E. P., Gutierrez, Á., Garcia, M. A., Latasa, P., Sancho, R., Mendioroz, J., Martinez-Marcos, M., Platón, E. M., Rivera, M. V. G., Pérez-Martinez, O., Álvarez-Gil, R., Wagner, E. R., Gonzalez-Coviella, N. L., Zornoza, M., . . . Collaborators, T. N. E. S. (2025). Effectiveness of catch-up and at-birth nirsevimab immunisation against RSV hospital admission in the first year of life: a population-based case–control study, Spain, 2023/24 season. Eurosurveillance, 30(5). https://doi.org/10.2807/1560-7917.es.2025.30.5.2400596

Principi, N., Perrone, S., & Esposito, S. (2025). Challenges and Limitations of Current RSV Prevention Strategies in Infants and Young Children: A Narrative Review. Vaccines, 13(7), 717. https://doi.org/10.3390/vaccines13070717

Respiratory syncytial virus (RSV) FAQs | NCIRS. (2026, 8 mei). https://ncirs.org.au/ncirs-fact-sheets-faqs-and-other-resources/respiratory-syncytial-virus-rsv-frequently-asked

RIVM. (z.d.-b). Respiratory syncytial virus (RSV) | RIVM. https://www.rivm.nl/en/rsv

RIVM. (2026, 19 maart). Significantly fewer babies in Dutch ICUs thanks to injection against RSV. https://www.rivm.nl/en/news/significantly-fewer-babies-in-dutch-icus-thanks-to-injection-against-rsv