The burden of influenza in England by age and clinical risk group: A statistical analysis to inform vaccine policy

Objectives: To assess the burden of influenza by age and clinical status and use this to inform evaluations of the age and risk-based influenza vaccination policy in the United Kingdom. Methods: Weekly laboratory reports for influenza and 7 other respiratory pathogens were extracted from the national database and used in a regression model to estimate the proportion of acute respiratory illness outcomes attributable to each pathogen. Results: Influenza accounted for similar to 10% of the attributed respiratory admissions and deaths in hospital. Healthy children under five had the highest influenza admission rate (1.9/1000). The presence of co-morbidities increased the admissionrate by 5.7 fold for 5-14 year olds (from 0.1 to 0.56/1000), the relative risk declining to 1.8 fold in 65+ year olds (from 0.46 to 0.84/1000). The majority (72%) of influenza-attributable deaths in hospital occurred in 65+ year olds with co-morbidities. Mortality in children under 15 years was low with around 12 influenza-attributable deaths in hospital per year in England; the case fatality rate was substantially higher in risk than non-risk children. Infants under 6 months had the highest consultation and admission rates, around 70/1000 and 3/1000 respectively. Conclusions: Additional strategies are needed to reduce the remaining morbidity and mortality in the high-risk and elderly populations, and to protect healthy children currently not offered the benefits of vaccination. (C) 2014 The Authors. Published by Elsevier Ltd on behalf of the The British Infection Association. All rights reserved.