Abstract
Seasonal influenza is usually considered an acute respiratory infection with a full recovery within a week. In addition to the traditional outcomes, there is now evidence of indirect effects in terms of neurological and functional complications. Major organ systems can be affected, underlining the need for preventative measures against infection. The aim of this podcast, featuring Dr. Ann Falsey, Dr. Stefania Maggi, and Dr. Tor Biering-Sørensen, is to outline influenza complications beyond acute respiratory disease, as well as discussing the need for quality of evidence when evaluating influenza vaccines. Assessing the benefits of vaccination can be challenging. To ensure a high quality of evidence, the innovative randomization of patients within the study design to avoid bias and the assessment of additional outcomes beyond immunogenicity as well as the inclusion of a broad population-including frail or vulnerable individuals-are essential. Studies leveraging nationwide registries such as the DANFLU-2 trial in Denmark highlight the advantages of a digitalized healthcare system for conducting large-scale randomized trials. Furthermore, large-scale trials such as the Gravenstein study have supplied a sizable body of evidence supporting the use of high-dose influenza vaccine in older adults. In conclusion, achieving a high quality of evidence is key for decision-making on seasonal influenza vaccines.