Clinical Report: RSV Prevention Tied to Lower Infant Acute Care Use

Overview

A cohort study in Washington state estimated a 43% relative decrease in respiratory syncytial virus (RSV)-associated hospitalizations and emergency department visits among infants aged 7 months or younger during the second year of routine use of nirsevimab and maternal vaccination, based on data from July 2022 to June 2025. The findings highlight the population-level impact of these preventive measures.

Background

Respiratory syncytial virus (RSV) is a leading cause of acute lower respiratory infections in infants, resulting in significant hospitalization rates. Effective prevention strategies, including monoclonal antibodies and maternal vaccination, are crucial to reduce the burden of RSV in vulnerable populations. Understanding the impact of these interventions can inform clinical practices and public health policies.

Data Highlights

Key Findings

• A 43% relative decrease in RSV-associated hospitalizations and emergency visits was observed among infants aged 7 months or younger during the second year of nirsevimab and maternal vaccination.
• The median age of RSV cases increased from 9 months in 2022-2023 to 12 months in 2024-2025, indicating a shift in disease burden.
• Population-level impact varied across counties in Washington, with decreases ranging from 15.5% to 57.7%.
• Uptake of preventive measures was limited by supply constraints, with only 39% of eligible infants immunized in the first season.
• Newly available clesrovimab may further enhance prevention strategies against RSV.
• Disparities in RSV hospitalization rates were noted among different racial groups, particularly affecting Native Hawaiian or Other Pacific Islander infants.

Clinical Implications

Healthcare providers should prioritize the administration of nirsevimab and maternal vaccination to eligible infants, particularly in underserved populations, to reduce RSV-related hospitalizations. Continuous monitoring of vaccination uptake and effectiveness is essential. The introduction of clesrovimab may provide additional options for prevention.

Conclusion

The study underscores the effectiveness of RSV prevention strategies in reducing hospitalizations among infants, highlighting the importance of continued vaccination efforts. Further evaluation of disparities in outcomes is warranted to ensure equitable access to preventive measures, especially with the introduction of new treatments like clesrovimab.

References

1. JAMA Pediatrics, 2023 -- RSV Antibody Prophylaxis Needs for Extremely Preterm Infants in Their Second RSV Season
2. The Journal of Infectious Diseases, 2023 -- Clinical Characteristics and In-hospital Outcomes Associated With Respiratory Syncytial Virus vs Other Viral Acute Lower Respiratory Infections in Hospitalized Children Younger Than 2 Years
3. The Journal of Infectious Diseases, 2023 -- Annual Clinical and Economic Burden of Medically Attended Lower Respiratory Tract Illnesses Due to Respiratory Syncytial Virus Among US Infants Aged <12 Months
4. CDC, 2025 -- RSV Immunization Guidance for Infants and Young Children
5. MMWR, 2025 -- Interim Evaluation of Respiratory Syncytial Virus Hospitalization Rates Among Infants and Young Children After Introduction of Respiratory Syncytial Virus Prevention Products
6. conexiant — Older RSV Hospitalization Linked to Pneumonia
7. CDC RSV Immunization Guidance
8. Interim Evaluation of Respiratory Syncytial Virus Hospitalization Rates Among Infants and Young Children After Introduction of Respiratory Syncytial Virus Prevention Products — United States, October 2024–February 2025 | MMWR