Background: Respiratory syncytial virus (RSV) can cause serious disease in infants, particularly those with high-risk (HR) conditions or born preterm. In the past 2 decades, interventions to prevent serious RSV disease have been implemented for these infants. This study assessed infant hospitalization trends for RSV and unspecified bronchiolitis (UB) by HR status and gestational age (GA) during the first year of life in a population-based cohort.
Methods: California hospital discharge data from the Office of Statewide Hospital Planning & Development linked to vital statistics for 1997–2011 was used to identify infants 17–47 weeks GA. Trends of RSV- and UB-coded hospital admissions during the first year of life were compared by GA category and by HR status (ICD-9 codes for chronic lung disease, congenital heart disease, and other conditions increasing risk of respiratory infection).
Results: Of 7,406,370 infants discharged after birth, 161,094 (2.2%) had HR status. In the HR cohort, 82,540 non-birth hospitalizations occurred, with 5,765 (7.0%) for RSV and 5,166 (6.3%) for UB. In non-HR infants, 737,326 non-birth hospitalizations occurred, with 99,378 (13.5%) for RSV and 72,442 (9.8%) for UB. For HR infants, RSV hospitalizations decreased from 1997 to 2010 (Fig. 1); the highest admission rates occurred in infants aged <3 mos. For non-HR infants overall, RSV hospitalization rates remained similar throughout the study period. UB hospitalization rates for HR infants were stable and decreased for non-HR infants. For non-HR preterm infants, RSV hospitalizations for all GA categories decreased, with greater decreases in those with earlier GA (Fig. 2), whereas UB hospitalization rates were relatively stable (Fig. 3).
Conclusion: RSV and UB hospitalizations are common in the first year of life. During the study period, admissions for RSV in non-HR infants and for UB in HR and non-HR infants remained stable from 1997 to 2010; however, admissions for RSV in HR and preterm infants decreased significantly, possibly due to prevention efforts targeting this population.
Study supported by AstraZeneca.
C. S. Ambrose, AstraZeneca: Employee , Salary
M. Bennett, AstraZeneca: Grant Investigator , Research grant