- patient admitted already under invasive mechanical ventilation; - patient admitted with severe acute respiratory syndrome and diagnosed with an etiologic agent other than sars-cov-2; - prior vitamin d supplementation (above 1000 iu/day); - renal failure requiring dialysis or creatinine ≥ 2.0mg/dl; - admitted patients with expected hospital discharge in less than 24 hours; - patient unable to sign the consent form.

- patient admitted already under invasive mechanical ventilation; - patient admitted with severe acute respiratory syndrome and diagnosed with an etiologic agent other than sars-cov-2; - prior vitamin d supplementation (above 1000 iu/day); - renal failure requiring dialysis or creatinine ≥ 2.0mg/dl; - admitted patients with expected hospital discharge in less than 24 hours; - patient unable to sign the consent form.