Influenza-related lower respiratory tract infection (LRTI) can cause serious illness or death in children younger than a year old. Only four medications are registered to treat influenza, and these do not have detailed recommendations for treating children younger than one year of age. One of these medications, oseltamivir, has no official recommendation for usage in children younger than one year of age, but it may be the best treatment for certain strains of influenza. A small number of children younger than one year of age have received oseltamivir in several countries with good clinical outcomes and apparently good tolerability. This study will test oseltamivir in children younger than one year of age to see if it is safe and effective.~Children younger than one year of age with influenza will be recruited for this study. Participants will receive the usual care for influenza with the addition of oseltamivir. Oseltamivir will be given orally for 5 days to children with human influenza, 7 days to children with H1N1 influenza in Vietnam, and 10 days to children with avian influenza. Participants will need to remain in the hospital between 5 and 12 days, depending on their illnesses.~Study assessments will be performed daily for 14 days with follow-up examinations occurring 1 to 2 weeks, 6 months, and 12 months after study entry. These assessments will include normal tests for children with influenza, such as blood tests and chest x-rays, but additional blood and nose, throat, and mouth samples will be collected for the study. Participants on a breathing machine will give lung samples.
Currently, there is no standard treatment for influenza with related lower respiratory tract infection (LRTI) in children younger than one year of age, even though influenza related LRTI is a potentially fatal illness in these children. This study will test a medicine for influenza in children younger than one year of age to see if it is safe and effective.