Influenza

METHODS AND OUTCOMES: We conducted a systematic review and aimed to answer the following clinical question: What are the effects of vaccines to prevent influenza? We searched: Medline, Embase, The Cochrane Library, and other important databases up to March 2011 (Clinical Evidence reviews are updated periodically; please check our website for the most up-to-date version of this review). We included harms alerts from relevant organisations such as the US Food and Drug Administration (FDA) and the UK Medicines and Healthcare products Regulatory Agency (MHRA). RESULTS: We found 9 systematic reviews, RCTs, or observational studies that met our inclusion criteria. We performed a GRADE evaluation of the quality of evidence for interventions. CONCLUSIONS: In this systematic review we present information relating to the effectiveness and safety of the following interventions: vaccines in adults, children, and older people. INTRODUCTION: During the autumn-winter months (influenza seasons), influenza circulates more frequently, causing a greater proportion of influenza-like illness and sometimes serious seasonal epidemics. The incidence of symptoms related to influenza as well as influenza-like illness depends on the underlying immunity of the population.