Background: Increasing use of rapid influenza diagnostics facilitates laboratory confirmation of influenza infections. We describe laboratory-confirmed, influenza-associated hospitalizations in a population representing almost 6% of children in the United States.
Methods: We conducted population-based surveillance for influenza-associated hospitalizations between October 1, 2003, and March 31, 2004, in 54 counties in 9 states (4.2 million children) participating in the Emerging Infections Program Network. Clinical characteristics, predictors of intensive care unit admission and geographic and age-specific incidence were evaluated.
Results: Surveillance identified 1,308 case-patients; 80% were <5 years and 27% were <6 months of age. Half of the patients and 4 of 5 pediatric deaths did not have a medical indication for influenza vaccination and were outside the 6- to 23-month age group. Twenty-eight percent of case-patients had radiographic evidence of a pulmonary infiltrate, 11% were admitted to intensive care and 3% received mechanical ventilation. The median length of hospital stay was 2 days. Community-acquired invasive bacterial coinfections (1% of patients) were associated with intensive care admission (adjusted odds ratio, 16.9; 95% confidence interval, 5.0–56.8). Thirty-five percent of patients ≥6 months old had received at least one influenza vaccine dose that season. The overall incidence of influenza-associated hospitalizations was 36 per 100,000 children (range per state, 10 per 100,000 to 86 per 100,000).
Conclusions: Influenza was an important cause of hospitalizations in children during 2003–2004. Hospitalizations were particularly common among children <6 months of age, a group for whom influenza vaccine is not licensed. Continued surveillance for laboratory-confirmed influenza could inform prevention strategies.
From the *National Center for Infectious Diseases, Centers for Disease Control and Prevention, Atlanta, GA; †Colorado Emerging Infections Program, Denver, CO; ‡Department of Human Services, Portland, OR; §Tennessee Department of Health and ∥Vanderbilt Medical Center, Nashville, TN; ¶Johns Hopkins Bloomberg School of Public Health, Baltimore, MD; #California Department of Health Services, Berkeley, CA; **Yale Emerging Infections Program, New Haven, CT; ††Department of Human Resources, Atlanta, GA; ‡‡Minnesota Department of Health, Minneapolis, MN; §§New York Department of Health, Albany, NY.
Accepted for publication November 23, 2005.
Supported by the Emerging Infections Program of the National Center for Infectious Diseases Office of the Director. The funder played no role in design and conduct of the study; collection, management, analysis, and interpretation of the data; and preparation, review, or approval of the manuscript.
Address for correspondence: Stephanie Schrag, Mailstop C23, Centers for Disease Control and Prevention, 1600 Clifton Road, NE, Atlanta, GA 30333; E-mail SSchrag@cdc.gov.