Clinical epidemiology and predictors of outcome in children hospitalised with influenza A(H1N1)pdm09 in 2009: A prospective national study.

Abstract

Background: There are few large-scale, prospective studies of influenza A(H1N1)pdm09 in children that identify predictors of adverse outcomes. Objective(s): We aimed to examine clinical epidemiology and predictors for adverse outcomes in children hospitalised with influenza A(H1N1)pdm09 in Australia. Method(s): Active hospital surveillance in six tertiary paediatric referral centres (June-September, 2009). All children aged <15 years admitted with laboratory-confirmed influenza A(H1N1)pdm09 were studied. Result(s): Of 601 children admitted with laboratory-confirmed influenza, 506 (84.2%) had influenza A(H1N1)pdm09. Half (51.0%) of children with influenza A(H1N1)pdm09 were previously healthy. Hospital stay was longer in children with pre-existing condition (mean 6.9 versus 4.9 days; P = 0.02) as was paediatric intensive care unit (PICU) stay (7.0 versus 2.3 days; P = 0.005). Rapid diagnosis decreased both antibiotic use and length of hospital and PICU stay. Fifty (9.9%) children were admitted to a PICU, 30 (5.9%) required mechanical ventilation and 5 (0.9%) died. Laboratory-proven bacterial co-infection and chronic lung disease were significant independent predictors of PICU admission (OR 6.89, 95% CI 3.15-15.06 and OR 3.58, 95% CI 1.41-9.07, respectively) and requirement for ventilation (OR 5.61, 95% CI 2.2-14.28 and OR 5.18, 95% CI 1.8-14.86, respectively). Chronic neurological disease was a predictor of admission to PICU (OR 2.30, 95% CI 1.14-4.61). Conclusion(s): During the 2009 pandemic, influenza was a major cause of hospitalisation in tertiary paediatric hospitals. Co-infection and underlying chronic disease increased risk of PICU admission and/or ventilation. Half the children admitted were previously healthy, supporting a role for universal influenza vaccination in children.Copyright © 2014 The Authors. Influenza and Other Respiratory Viruses Published by John Wiley & Sons Ltd.