Potential problem of the co-occurrence of pandemic COVID-19 and seasonal influenza

In times of COVID-19 pandemics, the upcoming period of the year when influenza activity usually increases in the Northern Hemisphere brings new medical and public health challenges. These challenges include the risk of mixed infections and/or a possible collision of the two epidemics ("twindemia") with a potentially serious impact on individual health and public health. In this report, we discuss the results of the published studies and conclude that the catastrophic collision of the seasonal influenza and COVID-19 epidemics is unlikely when efficient non-pharmaceutical public health measures are applied to control or mitigate the spread of the COVID-19 epidemic. This conclusion is supported by several lines of evidence, including the extremely low seasonal influenza activity registered in the Southern Hemisphere in 2020. On the other hand, the existence of mixed SARS-CoV-2 and influenza virus infections has been demonstrated in humans. The continuing uncertainty about the occurrence and potential severity of these mixed infections emphasizes the importance of seasonal influenza vaccination in the current epidemiological situation and raises the need to: (i) ensure vaccine availability, (ii) facilitate access to safe seasonal influenza vaccination under the conditions of the ongoing COVID-19 epidemic, and (iii) promote the vaccine to the public.