Several factors can influence the clinical severity in patients with COVID-19. Age is associated with elevated morbidity and mortality in patients with COVID-19 [112]. The elderly with COVID-19 (32%) have higher mortality rates compared with the middle-aged and the young [113]. The elderly with coexisting conditions, such as diabetes, hypertension, and obesity increase their mortality risk five-fold [114]. Oxidative stress and aging go hand in hand during coronavirus infection. Aging not only affects the immune response, but also induces a pro-inflammatory state. Aged-animals infected with SARS-CoV display more severe lesions and an increased pro-inflammatory response than their young counterparts [115]. This indicates that the age-associated accumulation of oxidative stress and a reduced antioxidative defense can worsen viral infections [116]. It is speculated that G6PD-deficient variants enhance the clinical severity of COVID-19. Hence, in the elderly with COVID-19, those with G6PD deficiency may become more anaemic than those with the normal activity of G6PD [117,118].