Influenza-related hospitalizations among young children in Leicestershire

Population-based data on influenza hospitalizations are unavailable in the United Kingdom, but they represent an essential component of health economic analyses that could support the use of vaccines and antiinfluenza drugs in healthy children. We collected data on hospitalizations for influenza infections among young children in Leicester, UK.

This prospective, longitudinal, noninterventional single center study was conducted at the Children's Hospital in Leicester, which provides inpatient pediatric care to a total population of approximately 1 million. We studied children <6 years of age between October 14, 2001, and June 30, 2002, who were admitted to the hospital with an acute respiratory tract illness, seizures, specified acute febrile gastrointestinal illness or any acute febrile illness or apnea or other life-threatening events in infants <12 months of age. Nasopharyngeal swabs obtained within 24 h of hospital admission were examined for influenza, respiratory syncytial virus and human metapneumovirus by PCR.

Of 7165 clinical episodes that were assessed in the Children's Hospital between October 1 and June 30, 2441 (34.1%) were caused by acute respiratory illness. Overall 33 (5.4%) of 613 children analyzed had an influenza A or B virus infection, including 19 (5.0%) of 381 children with acute respiratory illness and 14 (6.0%) of the remaining 232 children.

Influenza is evidently an important cause of hospitalization among young children, even during limited outbreaks of influenza. Further analyses will enable us to estimate age-related admission rates for influenza and to compare the burden from influenza with that for respiratory syncytial virus and human metapneumovirus.