What Is the True Burden of Influenza in Children?

Summary and Comment |
July 19, 2006

What Is the True Burden of Influenza in Children?

  1. Robert S. Baltimore, MD

The burden is substantial, yet most cases go undiagnosed, both in the doctor’s office and in the hospital.

  1. Robert S. Baltimore, MD

The CDC currently recommends routine influenza immunization for children aged 6–59 months (previously 6–23 months). But what is the actual disease burden of influenza among young children, and does it justify the CDC’s newly expanded recommendation? To find out, researchers determined the rates of influenza infection among children <5 years old who were living in one of three participating U.S. counties and receiving healthcare for symptoms of acute respiratory disease or fever. Hospitalized children were enrolled from 2000 through 2004; those visiting certain clinics and outpatient departments were enrolled during the 2002–2003 and 2003–2004 influenza seasons.

Among 2797 inpatient enrollees, influenza was confirmed by viral culture, PCR, or both in 6%, of whom 49% were <6 months old. Test results were not available to clinicians before patient discharge, so only 28% of all children and 43% of children in the intensive care unit who had influenza received a discharge diagnosis of influenza. The average annual hospitalization rate for laboratory-confirmed influenza was 0.9 per 1000 in children 0–59 months old and 4.5 per 1000 in those 0–5 months.

Influenza was confirmed in 274 of 1742 outpatient enrollees (16%). The percentage of children subsequently hospitalized was greatest, and the infection rate lowest, in those 0–5 months old. Only 17% of outpatients with laboratory-confirmed influenza received that diagnosis.


Influenza is generally underrecognized in young children, especially in outpatient settings, where youngsters with respiratory infections are usually treated. The authors and an editorialist note that such underrecognition represents missed opportunities for treatment and for prophylaxis of family contacts with antivirals. This article has received intense press coverage, with some suggesting that pediatricians’ failure to diagnose influenza represents substandard care. Many pediatricians counter that as a group, these undiagnosed children would not necessarily derive sufficient benefit from the diagnosis to justify the extra time and the cost of tests, and that significantly increasing antiviral use might cause rapid development of resistance to such agents. The study findings certainly support the current vaccination recommendations.


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