On Sept. 14, 2020, scientists at the Max Planck Institute for Infection Biology in Berlin and the Institut Pasteur in Paris used a mathematical model to study the first months of the corona pandemic in Europe. They showed that the decrease of Covid-19 cases in spring was not only related to countermeasures but also to the end of the flu season.

Influenza may have increased transmission of the coronavirus by an average of 2.5-fold. The results of the study suggested that the coming flu epidemic will have a amplifying impact on the Covid-19 pandemic. The researchers emphasized the potential importance of flu vaccinations as a possible extra protection against Covid-19. The study was pre-published on medRxiv and had not yet been peer reviewed.