Pediatric respiratory syncytial virus rehospitalization rate a retrospective observational study from Switzerland

Rupp N, Schobi N, Duppenthaler A, Casaulta C, Kopp MV, Agyeman PK, Aebi C. BMC Pediatr. 2025 Jul 12;25(1):550. doi:10.1186/s12887-025-05887-z.

Introduction

Respiratory Syncytial Virus (RSV) is a leading cause of severe respiratory infections and hospitalizations in young children worldwide, particularly those under two years of age. Recently, long-acting monoclonal antibodies have become available and are increasingly used for primary prevention of severe RSV disease. However, understanding the risk of rehospitalization after an initial severe RSV episode is critical to inform guidelines on secondary prevention strategies using these monoclonal antibodies.

This retrospective observational study from Switzerland analyzes 13 RSV seasons (2009-2023) in a large cohort to estimate the rates of rehospitalization after a primary RSV hospitalization, with particular attention to same-season rehospitalizations that would potentially justify additional doses of monoclonal antibodies.

Study Overview

This single-center retrospective cohort study utilized data collected from an ongoing RSV surveillance program spanning 13 consecutive seasons (2009-2023). The study included 3,143 patients with documented primary RSV hospitalization. Researchers assessed both the overall and same-season rehospitalization rates for patients of any age and specifically within the first five years of life. Clinical characteristics of rehospitalization cases were described, including length of hospital stay and presence of comorbidities.

• Design: Retrospective observational cohort study
• Population: 3,143 patients hospitalized with primary RSV infection
• Timeframe: RSV seasons from 2009 to 2023
• Endpoints: Overall and same-season RSV rehospitalization rates; length of stay; clinical risk factors

Key Findings

Among 3,143 patients with initial RSV hospitalization:

• The overall rehospitalization rate was 2.2% (69 cases; 95% CI: 1.73-2.79).
• Same-season rehospitalization was exceptionally rare at 0.06% (2 cases; 95% CI: 0.02-0.23).
• Among children aged 0 to 5 years, rehospitalization rates were similar: 2.3% overall and 0.04% same-season.
• Median length of stay for rehospitalizations was significantly shorter (4 days, IQR 3-6) than for primary hospitalizations (6 days, IQR 4-9; p < 0.0001).
• Most rehospitalized children had pre-existing conditions (68%) and a substantial proportion were born prematurely (40%).
• The rarity of same-season RSV rehospitalizations suggests routine administration of a monoclonal antibody dose for same-season secondary prevention is not warranted.
• Current Swiss guidelines likely cover the majority of children at risk for subsequent season rehospitalizations by targeting those with pre-existing conditions.

Evidence Synthesis & Related Research

The strikingly low rate of same-season RSV rehospitalization (0.06%) reported by Rupp et al. aligns with and reinforces the argument against routine secondary prophylaxis with monoclonal antibodies within the same season. This complements findings from key studies:

• Moline et al., 2024 demonstrated high real-world effectiveness (90%) of nirsevimab in preventing initial RSV-related hospitalization, establishing the potency of monoclonal antibodies for primary prevention (PMID: 38457312).
• Yeoh et al., 2025 reported that children hospitalized with RSV had a significantly higher risk of respiratory-related rehospitalization over 1.5 years compared to those hospitalized for influenza or human metapneumovirus infections (PMID: 40295207), emphasizing increased longer-term morbidity post-RSV.

Interpretation: While same-season reinfection and rehospitalization is extremely rare and does not support routine same-season secondary prevention, the initial RSV hospitalization marks children as higher risk for subsequent respiratory morbidity. This highlights the importance of effective primary prevention strategies and targeted secondary prevention for children with pre-existing conditions as currently recommended in Switzerland.

Clinical Implications

• Routine administration of monoclonal antibodies for secondary same-season RSV prevention is not generally supported by current evidence given the rarity of same-season rehospitalizations.
• Primary prevention with monoclonal antibodies such as nirsevimab remains critical given its proven high effectiveness against first RSV hospitalization.
• Children rehospitalized tend to have pre-existing conditions or prematurity; thus, targeted secondary prevention protocols focusing on these high-risk groups align with current Swiss guidelines and should be maintained.
• Clinicians should consider longer-term monitoring and preventive strategies for children after initial RSV hospitalization due to increased risk of respiratory morbidity beyond the first season.

Strengths & Limitations

Future Directions

Prospective studies are needed to evaluate the direct efficacy and safety of monoclonal antibodies specifically for same-season secondary prevention in children after a severe first RSV episode. Further research should identify clinical and biological risk factors that predispose to rare same-season reinfections and explore tailored secondary prophylaxis strategies for high-risk pediatric subgroups.

Conclusion

Same-season RSV rehospitalizations are exceedingly rare, and routine monoclonal antibody dosing for secondary prevention within the same season is not generally warranted, though targeted prophylaxis for high-risk children remains essential.

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References

1. Moline HL, Tannis A, Toepfer AP, Williams JV, Boom JA, Englund JA, et al. Early estimate of nirsevimab effectiveness for prevention of respiratory syncytial virus-associated hospitalization among infants entering their first respiratory syncytial virus season – New Vaccine Surveillance Network, October 2023-February 2024. MMWR Morb Mortal Wkly Rep. 2024 Mar 7;73(9):209-214. doi: 10.1585/mmwr.mm7309a4. PMID: 38457312.
2. Yeoh SB, Vidler SI, Cohen JM, Moore HC, Bosch J, Jia Y, et al. Respiratory virus-associated hospitalisation and risk of readmission in children: a population-based cohort study. Lancet Respir Med. 2025. Published online July 1, 2024. doi: 10.1016/S2213-2600(24)00216-9. PMID: 40295207.
3. Rupp N, Schobi N, Duppenthaler A, Casaulta C, Kopp MV, Agyeman PK, Aebi C. Pediatric respiratory syncytial virus rehospitalization rate a retrospective observational study from Switzerland. BMC Pediatr. 2025 Jul 12;25(1):550. doi:10.1186/s12887-025-05887-z.