Quercetin, for its crucial properties, fulfills the need for a multifactor action that is useful for the potential counterbalance of a COVID-19 infection. Given this background, the aim of the study was to evaluate the potential effect of 3 months’ supplementation with Quercetin Phytosome® (250 mg twice a day) as prevention against symptomatic COVID-19. In total, 120 subjects were enrolled ( [...]