VEGFA and COVID-19: In severe cases of COVID-19, HIF-1α activation can lead to a cytokine storm (described below) by activation and stabilisation of immune cells including macrophages and neutrophils, causing the production of high amounts of inflammatory cytokines, vascular leakage (by up-regulation of the VEGF) and destruction of the alveolar-interstitial-endothelial epithelial complex barriers [40].