Seasonal influenza vaccine effectiveness in people with asthma: A systematic review

Introduction: Influenza is a respiratory infection that can cause mild to severe illness in people with asthma. Seasonal influenza vaccination is a preventable measure to prevent severe exacerbation of asthma. However, the effectiveness of influenza vaccination against influenza-related complications is still not established in people with asthma. Aim and objectives: To evaluate of the effectiveness of seasonal influenza vaccination in people with asthma. Methods: All published literature from 1970 to 2016 was systematically searched through electronic databases for experimental and observational studies on influenza vaccine efficacy and effectiveness in people with asthma. In addition, reference lists and citations were searched and vaccine companies contacted for the identification of further unpublished or ongoing studies. We present preliminary results on data extraction and quality appraisal performed by the first reviewer. Preliminary results: Nineteen randomised controlled trials (RCTs), six non-randomised trials and ten observational studies met the inclusion criteria. Most studies took place in Europe and the USA and approximately half of them included children as subjects. The inactivated influenza vaccine was the intervention used in more than half of the studies and the main reported outcomes were asthma exacerbation, adverse reactions after vaccination and healthcare utilisation. The risk of bias was low in eight of the RCTs. The quality ofevidence was strong in ten non-RCTs/observational. Conclusions: Separate meta-analyses for experimental and observational studies will be carried out to explore the protective and/or adverse effects of influenza vaccine in people with asthma.