Severe RSV disease in 2022–2023 was most likely to occur in infants under 6 months and older children with pulmonary or neurologic conditions.
A multicenter cohort study from 2 Canadian pediatric hospitals found that severe respiratory syncytial virus (RSV) disease during the 2022–2023 season disproportionately affected infants younger than 6 months and older children with certain underlying conditions. These findings, published in JAMA Network Open, offer updated risk profiles that may inform RSV prevention strategies, particularly in the era of newly available monoclonal antibody therapies.1
Following a sharp decline in RSV transmission during the COVID-19 pandemic, a resurgence of out-of-season RSV-associated acute respiratory infections (ARIs) overwhelmed pediatric hospitals in 2022 and 2023.1,2 Previous studies primarily focused on risk factors in infants, but shifts in age distribution and disease severity prompted researchers to reassess risk.
“Severe RSV-associated ARI was observed across all age groups among children with or without comorbid conditions,” the study authors wrote.1
The retrospective observational study included 709 children younger than 18 years hospitalized with microbiologically confirmed RSV-associated ARI from July 1, 2022, to June 30, 2023, at The Hospital for Sick Children in Toronto and BC Children’s Hospital in Vancouver. The median patient age was 13.1 months, and 62.3% were male. Most patients (63.8%) were under age 2, and 41.0% were transferred from another facility.
Severe disease—defined as requiring noninvasive or invasive ventilation or resulting in death—was identified in 28.8% of patients. One-third of patients required ICU admission.
Risk factors varied significantly between children under 2 years and those aged 2 years or older. "Among those younger than 2 years, those younger than 3 months (adjusted risk ratio [ARR], 2.34 [95% CI, 1.43-3.84]) and those aged 3 to less than 6 months (ARR, 2.79 [95% CI, 1.65-4.70]) both had increased risk of severe disease vs those aged 1 to less than 2 years," wrote the authors, who added prematurity also increased the risk for severe disease (ARR, 1.40).
In children aged 2 years or older, the presence of pulmonary disease and/or use of home oxygen was associated with a 2.47 ARR of severe RSV disease. Neurologic, neuromuscular, or developmental conditions were also associated with elevated risk (ARR, 1.89). Notably, children aged 5 to <18 years had the highest risk in this group compared with those aged 2 to 4 years (ARR, 1.79 [95% CI, 1.06-3.00]).
Of all patients, 26.8% required noninvasive ventilation, and 9.3% required invasive mechanical ventilation. Over half of those needing respiratory support were younger than 3 months. ICU admission occurred in 34.0% of cases, and the median length of stay was 3 days for both overall and ICU admissions. One patient died.
Shorter symptom duration prior to admission was also linked to increased disease severity and ICU admission, suggesting rapid clinical decline in high-risk children.
The findings support the continued rollout of preventive tools such as the monoclonal antibody nirsevimab in infants, especially those under 6 months or with a history of prematurity. The data also suggest that children aged 2 years and older with specific chronic conditions may benefit from targeted protection strategies.
“Health systems moving toward universal prevention in infancy may consider the added benefit of monoclonal antibody therapies for older high-risk children,” the authors concluded. “Continued surveillance of RSV-associated ARI in the postpandemic era will help determine whether these observed changes in patient epidemiologic characteristics are transient or indicative of a lasting change."
References
1. Kirolos N, Mtaweh H, Datta RR, et al. Risk Factors for Severe Disease Among Children Hospitalized With Respiratory Syncytial Virus. JAMA Netw Open. 2025;8(4):e254666. doi:10.1001/jamanetworkopen.2025.4666
2. Principi N, Autore G, Ramundo G, Esposito S. Epidemiology of respiratory infections during the COVID-19 pandemic. Viruses. 2023;15(5):1160. doi:10.3390/v15051160
