Background: Respiratory syncytial virus (RSV) causes significant morbidity in children and is the most common cause of bronchiolitis. Hasegawa et al (Pediatrics 2013) recently described a 21% decline in the US infant bronchiolitis hospitalization rate from 2000 to 2009, with a concomitant 34% increase in the proportion of hospitalized children with high-risk medical conditions. Bronchiolitis rates in high-risk children were not described. The objective of this study was to examine national trends in RSV and unspecified bronchiolitis (UB) hospitalization rates from 19972012 among high-risk infants.
Methods: The Kids' Inpatient Database (KID) infant annual hospitalization rates for RSV (ICD-9 codes 079.6, 466.11, 480.1) and UB (ICD-9 code 466.19) were estimated using weighted counts. Denominators were based on weighted counts of newborn hospitalizations with high-risk conditions: chronic respiratory disease arising in the perinatal period (chronic lung disease [CLD]); congenital airway anomalies; cystic fibrosis; higher-risk congenital heart disease (CHD); lower-risk CHD; neuromuscular disease; Down syndrome; HIV; immunodeficiency; and other genetic, metabolic, and musculoskeletal conditions. Preterm infants could not be identified because of infrequent use of preterm codes. Poisson regression was used to test for statistical significance of trends.
Results: Among nonhigh-risk infants, hospitalization rates declined for RSV (change from 1997 to 2012: 9.8%; Ptrend < 0.001) and UB (33.8%; P< 0.001). Among high-risk infants, RSV hospitalization rates declined (36.9%; P< 0.001), but UB hospitalization rates did not (+0.7%; P=0.709). Trends varied by specific high-risk group (Figures).
Conclusion: Among US high-risk infants from 1997 to 2012, RSV hospitalizations declined but UB hospitalizations did not. RSV hospitalization rates declined due to rate decreases among CLD and CHD infants, which coincided with widespread RSV immunoprophylaxis of these populations. No declines were observed in other high-risk groups. UB hospitalization rates increased in all groups except for higher-risk CHD.
Figure 1. RSV Hospitalization Rates in Infants with High-Risk Conditions in the KID, 1997‒2012
Figure 2. UB Hospitalization Rates in Infants with High-Risk Conditions in the KID, 1997‒2012
J. P. Fryzek,
X. Jiang, EpidStat Institute: Research Contractor , Research grant
J. E. Coalson, EpidStat Institute: Research Contractor , Research grant
K. K. Mclaurin, AstraZeneca: Employee , Salary
C. S. Ambrose, AstraZeneca: Employee and Shareholder , Salary