RSV Hospital Admissions During the First 2 Seasons Among Children With Chronic Medical Conditions

National Immunization Technical Advisory Groups recommend long-acting monoclonal antibody prophylaxis for the prevention of respiratory syncytial virus (RSV) disease for children at high risk in the first season, regardless of RSV vaccination during pregnancy, and for those who remain at increased risk in the second season.

This study assessed which groups of children with chronic medical conditions (CMCs) are at higher risk of RSV hospitalization during their first and second RSV seasons.

This retrospective, population-based, season-stratified cohort analysis was conducted among children who were born between April 1, 2013, and March 31, 2023, in British Columbia, Canada (population of 5.7 million in 2024), and were enrolled in the provincial medical service plan and followed up until the day before their third RSV season or April 1, 2024, whichever occurred first.

Any CMC diagnosed in the first 2 years of life.

Respiratory syncytial virus-related hospitalizations.

The final cohort consisted of 431 937 children (32 959 [7.6%] born at <37 weeks' gestation; 222 207 boys [51.4%]) followed up for a median of 728 days (IQR, 642-729 days), including 25 452 children (5.9%) diagnosed with at least 1 of 1116 distinct CMCs. In total, 4567 children (1.1%) experienced a combined total of 4592 RSV hospitalizations, combining data from the first and second RSV seasons. In the first RSV season, the RSV hospitalization rate per 1000 person-years for children with CMCs was 15.9 (95% CI, 14.2-17.6) and for children without CMCs was 8.0 (95% CI, 7.7-8.3). In the second RSV season, the RSV hospitalization rate per 1000 person-years for children with CMCs was 7.8 (95% CI, 6.7-8.8) and for children without CMCs was 2.2 (95% CI, 2.1-2.3). Children with multisystem CMCs, particularly those affecting the respiratory, cardiovascular, or gastrointestinal systems, had second-season RSV hospitalization rates that were at least 2-fold higher than the rate among all children in the first season. Second-season rates among children with Down syndrome or those who were born prematurely (<28 weeks of gestation) were 5-fold higher than for all children in the first season.

This population-based retrospective cohort study identified specific groups of higher-risk children with CMCs who could most benefit from prophylaxis with long-acting monoclonal antibodies in their first and second RSV seasons. This study supports expanded eligibility criteria for long-acting monoclonal antibody prophylaxis.