Overall, these data confirm previous similar studies [16–22] and demonstrate on a prospective setting that vitamin D deficiency is associated with the clinical outcomes of COVID-19, independently of inflammatory markers (e.g. IL-6 and CRP), age, or the presence of major comorbidities such as obesity, diabetes and hypertension, that are commonly observed among hospitalized COVID-19 patients. Here, IL6 is linked to COVID-19.