Respiratory Syncytial Virus–Associated Hospitalizations Among Children Less Than 24 Months of Age

TLDR

RSV is a leading cause of infant hospitalization, but burden estimates have been imprecise due to coarse age stratification, underscoring the need for broad preventive strategies for all young infants. We analyzed data from a 5‑year, prospective, population‑based surveillance of young children hospitalized with laboratory‑confirmed RSV acute respiratory illness during October–March 2000‑2005, stratifying the at‑risk population by month of age using birth certificate data to derive hospitalization rates. Among 2,149 hospitalized ARI children, 559 (26%) had RSV, yielding an overall rate of 5.2 per 1,000 <24‑month‑old infants, peaking at 25.9 per 1,000 in 1‑month‑olds; 44% of RSV cases were ≤2 months old with a rate of 17.9 per 1,000, 79% were previously healthy, and very preterm infants had threefold higher rates than term infants.

Abstract

Respiratory syncytial virus (RSV) infection is a leading cause of hospitalization among infants. However, estimates of the RSV hospitalization burden have varied, and precision has been limited by the use of age strata grouped in blocks of 6 to ≥ 12 months.We analyzed data from a 5-year, prospective, population-based surveillance for young children who were hospitalized with laboratory-confirmed (reverse-transcriptase polymerase chain reaction) RSV acute respiratory illness (ARI) during October through March 2000-2005. The total population at risk was stratified by month of age by birth certificate information to yield hospitalization rates.There were 559 (26%) RSV-infected children among the 2149 enrolled children hospitalized with ARI (85% of all eligible children with ARI). The average RSV hospitalization rate was 5.2 per 1000 children <24 months old. The highest age-specific rate was in infants 1 month old (25.9 per 1000 children). Infants ≤ 2 months of age, who comprised 44% of RSV-hospitalized children, had a hospitalization rate of 17.9 per 1000 children. Most children (79%) were previously healthy. Very preterm infants (<30 weeks' gestation) accounted for only 3% of RSV cases but had RSV hospitalization rates 3 times that of term infants.Young infants, especially those who were 1 month old, were at greatest risk of RSV hospitalization. Four-fifths of RSV-hospitalized infants were previously healthy. To substantially reduce the burden of RSV hospitalizations, effective general preventive strategies will be required for all young infants, not just those with risk factors.