Epidemiology and Infection

Research Article

Estimating the undetected burden of influenza hospitalizations in children

C. G. GRIJALVAa1, G. A. WEINBERGa6, N. M. BENNETTa7a8, M. A. STAATa9, A. S. CRAIGa1a10, W. D. DUPONTa4, M. K. IWANEa11, A. S. POSTEMAa12, W. SCHAFFNERa1a2, K. M. EDWARDSa3 and M. R. GRIFFINa1a2a5 c1

a1 Department of Preventive Medicine, Vanderbilt University School of Medicine, Nashville, TN, USA

a2 Department of Medicine, Vanderbilt University School of Medicine, Nashville, TN, USA

a3 Department of Pediatrics, Vanderbilt University School of Medicine, Nashville, TN, USA

a4 Department of Biostatistics, Vanderbilt University School of Medicine, Nashville, TN, USA

a5 Center for Education and Research on Therapeutics, Vanderbilt University School of Medicine, Nashville, TN, USA

a6 Department of Pediatrics and Strong Children's Research Center, Rochester, New York, NY, USA

a7 Center for Community Health and Department of Medicine, University of Rochester School of Medicine & Dentistry, Rochester, New York, NY, USA

a8 Monroe County Department of Public Health, Rochester, New York, NY, USA

a9 Department of Pediatrics, Cincinnati Children's Hospital Medical Center, University of Cincinnati College of Medicine, Cincinnati, OH, USA

a10 The Tennessee Department of Health, Nashville, TN, USA

a11 The National Immunization Program, Centers for Disease Control and Prevention, Atlanta, GA, USA

a12 The National Center for Infectious Diseases, Division of Viral and Rickettsial Diseases, Influenza Branch, Centers for Disease Control and Prevention, Atlanta, GA, USA

SUMMARY

During the 2004–2005 influenza season two independent influenza surveillance systems operated simultaneously in three United States counties. The New Vaccine Surveillance Network (NVSN) prospectively enrolled children hospitalized for respiratory symptoms/fever and tested them using culture and RT–PCR. The Emerging Infections Program (EIP) and a similar clinical-laboratory surveillance system identified hospitalized children who had positive influenza tests obtained as part of their usual medical care. Using data from these systems, we applied capture–recapture analyses to estimate the burden of influenza related-hospitalizations in children aged <5 years. During the 2004–2005 influenza season the influenza-related hospitalization rate estimated by capture–recapture analysis was 8·6/10 000 children aged <5 years. When compared to this estimate, the sensitivity of the prospective surveillance system was 69% and the sensitivity of the clinical-laboratory based system was 39%. In the face of limited resources and an increasing need for influenza surveillance, capture–recapture analysis provides better estimates than either system alone.

(Accepted October 19 2006)

(Online publication December 07 2006)

Correspondence:

c1 Author for correspondence: M. R. Griffin, M.D., M.P.H., A-1110 Medical Center North, Preventive Medicine Department, Vanderbilt University Medical Center, Nashville, TN 37232-2637, USA. (Email: marie.griffin@vanderbilt.edu)

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