On the other hand, vitamin D3 was found to attenuate the effects of these interactions between SARS-CoV-2 and the renin–angiotensin–aldosterone system (RAAS) (Giménez et al., 2020), where it acts as a negative endocrine regulator which protects against acute lung injury and acute respiratory failure (Malek Mahdavi, 2020). Here, REN is linked to respiratory failure.