Objective: To describe the influenza-related morbidity and mortality in healthy children aged under 5 years in South Australia, in order to further understand the potential role of influenza vaccination.

Design and setting: We undertook a descriptive analysis of SA hospital separations data and Australian Bureau of Statistics death data for children aged under 5 years admitted to hospital for influenza. All diagnoses related to an influenza admission were examined to determine whether children were at risk of complications from influenza, according to the criteria of the National Health and Medical Research Council.

Main outcome measures: Mean influenza admission rates per 100 000 population per year in children aged under 5 years between 1996 and 2006, and the proportion of children admitted to hospital who did not have a secondary diagnosis putting them at higher risk of influenza-related complications.

Results: From 1996 to 2006, 649 children aged under 5 years were admitted to hospital for influenza. Mean annual admission rates per 100 000 were highest in children aged under 1 year (151.0), and decreased with age. Aboriginal and Torres Strait Islander children aged under 5 years had a mean admission rate of 161.8 per 100 000. Most children under 5 years (81%) admitted to hospital did not have an underlying illness that would put them at risk of influenza-related morbidity.

Conclusion: Healthy children aged under 2 years and Aboriginal and Torres Strait Islander children under 5 years old have high rates of hospital admission, which may have implications for the target group recommendations for influenza immunisation. Currently, vaccination is recommended only for children with specified chronic diseases.