Effectiveness of influenza vaccine for the prevention of asthma exacerbations.

BACKGROUND There is a lack of clinical evidence that annual vaccination against influenza prevents asthma exacerbations in children. METHODS Retrospective cohort study of 800 children with asthma, where one half did, and the other half did not receive the influenza vaccine. The two groups were compared with respect to clinic visits, emergency department (ED) visits, and hospitalisations for asthma. In multivariable analyses, adjustment was made for baseline asthma severity, prior utilisation of health services, receipt of vaccine in the previous year, and demographic variables. RESULTS After adjusting for other variables, the vaccine group had a significantly increased risk of asthma related clinic visits and ED visits (odds ratios 3.4 and 1.9, respectively). CONCLUSION This study failed to provide evidence that the influenza vaccine prevents paediatric asthma exacerbations.