Coronavirus disease 2019 (COVID-19) was declared an emergency public health problem by the World Health Organization (WHO) in March 2020. Since then, several initiatives by the medical and scientific community have sought alternatives to treat infected individuals, as well as identifying risk or protective factors for the contamination and prognosis of patients. In this perspective, vitamin D supplementation can improve some important outcomes in critically ill patients, being considered a potent immunomodulatory agent. Vitamin D deficiency is a common outcome in critically ill patients, thus making it a modifiable risk factor with great potential for reducing hospital stay and intensive care and mortality. The investigators speculate that vitamin D supplementation could have therapeutic effects in patients with COVID-19.

Inclusion Criteria:

• Diagnosis of flu syndrome with hospitalization criteria;
• Respiratory rate ≥ 24irpm and / or saturation <93% in room air, or belonging to the risk group for complications: 1. Chronic diseases: heart disease, diabetes mellitus, systemic arterial hypertension and neoplasms, 2. Immunosuppression, 3. Pulmonary tuberculosis; 4. Obesity;
• Tomographic findings compatible with coronavirus disease.

Exclusion Criteria:

• 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.