Influenza-Associated Pneumonia in Children Hospitalized With Laboratory-Confirmed Influenza, 2003-2008

Background: Pneumonia is one of the most common complications in children hospitalized with influenza. We describe hospitalized children with influenza-associated pneumonia and associated risk indicators. Methods: Through Emerging Infections Program Network population-based surveillance, children aged <18 years hospitalized with laboratory-confirmed influenza with a chest radiograph during hospitalization were identified during the 2003-2008 influenza seasons. A case with radiologically confirmed influenza-associated pneumonia was defined as a child from the surveillance area hospitalized with: (1) laboratory-confirmed influenza and (2) evidence of new pneumonia on chest radiograph during hospitalization. Hospitalized children with pneumonia were compared with those without pneumonia by univariate and multivariate analysis. Results: Overall, 2992 hospitalized children with influenza with a chest radiograph were identified; 1072 (36%) had influenza-associated pneumonia. When compared with children hospitalized with influenza without pneumonia, hospitalized children with influenza-associated pneumonia were more likely to require intensive care unit admission (21% vs. 11%, P < 0.01), develop respiratory failure (11% versus 3%, P < 0.01), and die (0.9% vs. 0.3% P = 0.01). In multivariate analysis, age 6 to 23 months (adjusted OR: 2.1, CI: 1.6-2.8), age 2 to 4 years (adjusted OR: 1.7, CI: 1.3-2.2), and asthma (adjusted OR: 1.4, CI: 1.1-1.8) were significantly associated with influenza-associated pneumonia. Conclusions: Hospitalized children with influenza-associated pneumonia were more likely to have a severe clinical course than other hospitalized children with influenza, and children aged 6 months to 4 years and those with asthma were more likely to have influenza-associated pneumonia. Identifying children at greater risk for influenza-associated pneumonia will inform prevention and treatment strategies targeting children at risk for influenza complications.