Moreover, a wide variation in the severity of SARS-CoV2 infection’s clinical presentation has been noticed, ranging from absent or minimal symptoms to critical conditions and death. To date, although some risk factors have been identified (age, co-morbidities, etc.), it is not yet completely understood why some patients develop more severe symptoms than others. Considering our knowledge on the role of vitamin D in modulating the immune system and in inhibiting a hyper activation of the inflammatory response, together with data from observational and clinical studies on vitamin D supplementation, various authors have also suggested a potential role of vitamin D in reducing the severity of the disease [183,184,185,186,187]. Vitamin D is especially known for its ability to reduce the “cytokine storm” that contributes to the pathogenesis of various viral infections, including COVID-19 [188].