Table 1. Characteristics of studies selected.
Author Country Study Design Follow-up Population Age (years) Outcomes Sample Size Exposure or Intervention (n/cut-off or dose) Confounder adjusted
Abrishami et al
Iran
retrospective Cohort
February 28, 2020 and April 19, 2020
Hospitalized patients with COVID-19
55.18±14.98
Death and hospitalization
73
Vitamin D ≤25ng/mL
Age, sex, BMI, and comorbidities
Alguwaihes et al
Saudi Arabia
retrospective Cohort
May to July 2020
Hospitalized adults with COVID-19
55 (19–101)*
Mortality, ICU admission and NVI
150
112 (Vitamin D ≤12ng/mL)
Age, sex, BMI, smoking, comorbidities, serum vitamin D, use of medications, HbA1c, Neutrophil count, Creatinine and ALT.
Annweiler, C et al
France
Quasi-experimental study
March-April 2020
Frail elderly nursing-home residents with COVID-1
87.7 ± 9.0
Mortality of COVID-19 and clinical improvement
66
57 80,000 IU vitamin D3 either in the week following the suspicion or diagnosis of COVID-19, or during the previous month
Age, gender, number of drugs daily taken, functional abilities, nutritional status, COVID-19 treatment with corticosteroids and/or hydroxychloroquine and/or dedicated antibiotics, and hospitalization for COVID-19
Annweiler, G et al
France
Quasi-experimental study
March–May 2020
Patients hospitalized with COVID-19 in geriatric acute care unit
88 (85–92)*
14-Day COVID-19 Mortality and clinical improvement
77
Group 1 (n=29): Regular Vitamin D Supplementation Group 2 (n=16): Vitamin D Supplementation After COVID-19 Diagnosis
Age, gender, functional abilities, severe undernutrition, history of cancer, hypertension, cardiomyopathy, glycated hemoglobin, number of acute health issues at admission, hospital use of antibiotics, use systemic corticosteroids, and pharmacological treatments of respiratory disorders
Baktash et al
UK
Prospective cohort
1 March to 30 April 2020
Hospitalized patients aged ≥65 years with COVID-19
Mortality secondary to COVID-19; NIV support and admission to HDU, COVID-19 radiographic changes on chest X-ray
70
39 (Vitamin D ≤12ng/mL) Vitamin D; CRP, D-dimer, ferritin, high sensitivity troponin T, LDH and lymphocyte count. Age, weight, height, ethnicity, smoking status and comorbidities
Carpagnano et al
Italy
retrospective cohort
11 March to 30 April, 2020
COVID-19 hospitalized patients
65±13
Survival
42
10 (Vitamin D ≤ ≤10ng/mL)
Demographic characteristics, medical history, underlined comorbidities, symptoms, laboratory findings, respiratory parameters as fraction of inspired oxygen (FiO2) and arterial partial pressure oxygen PaO2/FiO2 ratio, respiratory and pharmacological treatment.
Castillo et al
Spain
Parallel pilot randomized open label, double-masked clinical trial
calcifediol,
Hospitalized patients with COVID-19 i
53 ± 10
ICU admission and deaths
76
50 Treatment group 20000-IU in admission (10000-IU on days 3 and 7)
Age, comorbidity, CRP, D-Dimer, LDH, Lymphocytes, Ferritin, IL-6
Cereda et al
Italy
cohort
March - April 2020
Hospitalized patients with COVID-19 i
77 (65.0-85.0)*
Mortality
129
99 (Vitamin D <20 ng/mL)
Age, gender, BMI, comorbidities, severe pneumonia, serum level of vitamin D, calcium, phosphorus, magnesium, D-Dimer, sodium, potassium, ALT, AST, LDH, CK, CRP, lymphocytes and platelets.
Hernández et al
Spain
case-control
hospitalized patients aged ≥18 years with confirmed COVID-19
61.0 (47.5-70.0)*
COVID-19 severity (death and ICU admission)
197
162 (Vitamin D ≤ ≤20ng/mL)
Age, sex, BMI, smoking, comorbidities, CRP. GFR, death, ICU, 25OHD and PTH
Jain et al
India
Prospective cohort
6 weeks
Patients with COVID-19
Serum IL-6, serum TNF-α, serum ferritin and serum level of vitamin D
154
90 (Vitamin D <20 ng/mL)
Age, gender, comorbidity, BMI, mortality, asymptomatic patients and critically patients
Macaya et al
Spain
retrospective cohort
March 5 to March 31, 2020
COVID-19 hospitalized patients
Non-severe COVID-19: 63 (50-72)* Severe COVID-19: 75 (66-84)*
COVID-19 severity (death, admission to ICU, and/or NVI)
80
45 (Vitamin D ≤ ≤20ng/mL)
Age, gender, obesity, cardiac disease, kidney disease, and vitamin D
Mendy et al (preprint)
USA
retrospective cohort
March 13, 2020 to May 31, 2020
Patients with COVID-19
49.5 (35.2- 67.5)*
Hospitalization and disease severity (ICU and/or death)
689
89 (Vitamin D <12 ng/mL) Age, sex, race/ethnicity, smoking, comorbidities
Merzon et al
Israel
retrospective Cohort
February 1 to April 30, 2020
Patients tested for COVID-19
COVID-19 group: 35.58 (34.49-36.67)** Non-COVID-19 group: 47.35 (46.87–47.85)**
Risk of COVID-19 and hospitalization
782 COVID-19 group 703 (Vitamin D ≤30ng/mL)
Age, sex, BMI, smoking and comorbidities
Pizzini et al
Austria
Prospective cohort
8 weeks
COVID-19 hospitalized patients and outpatients with persistent symptoms
58 ± 14
Severity and persistent cardio-pulmonary damage of COVID-19 patients
109
41 (Vitamin D <12 ng/mL)
Age, gender, comorbidity, BMI, vitamin D supplementation e and serum level of vitamin D, PTH, calcium, phosphate, creatinine, urea, CRP, interleukin-6, serum ferritin, and D-dimer
Radujkovic et al
Germany
Prospective cohort
18 Marchto 18 June 2020
Inpatients and Outpatients diagnosed with COVID-19
NVI and survival
185
41 (Vitamin D <12 ng/mL)
Age, gender, comorbidity, vitamin D supplementation e and serum level of vitamin D
Smet et al
Belgium
retrospective cohort
March 1, 2020, to April 7, 2020
Hospitalized patients with COVID-19 i
COVID-19 severity (stage disease and death)
186
109 (Vitamin D <20 ng/mL)
Age, sex, and comorbidities.
Tan et al
China
retrospective cohort
January 15 and April 15, 2020
hospitalized patients ≥50 y of age with COVID-19
Treatmente group:58.4 ±7 Control group: 64.1 ±7.9
Requiring oxygen therapy or ICU
43
17 1000-IU dose of vitamin D3 (cholecalciferol),
Age, sex, clinical features and comorbidities. Use of magnesium oxide, and vitamin B12 (methylcobalamine).
25OHD: 25-hydroyvitamin D, ALT: alanine transaminase, AST: aspartate aminotransferase, BMI: body-mass index, CK: creatine kinase, CRP: C reactive protein, GFR: glomerular filtration rate, HDU: High dependency unit, IL-6: interleukin-6; ICU: Intensive Care Unit, LDH: lactate dehydrogenase, NVI: Non-invasive ventilation, PCT: procalcitonin, PTH: parathyroid hormone. * Data represented as median (IQR). ** Data represented as mean (CI 95%) 25OHD: 25-hydroyvitamin D, ALT: alanine transaminase, AST: aspartate aminotransferase, BMI: body-mass index, CK: creatine kinase, CRP: C reactive protein, GFR: glomerular filtration rate, HDU: High dependency unit, IL-6: interleukin-6; ICU: Intensive Care Unit, LDH: lactate dehydrogenase, NVI: Non-invasive ventilation, PCT: procalcitonin, PTH: parathyroid hormone. * Data represented as median (IQR). ** Data represented as mean (CI 95%) 25OHD: 25-hydroyvitamin D, ALT: alanine transaminase, AST: aspartate aminotransferase, BMI: body-mass index, CK: creatine kinase, CRP: C reactive protein, GFR: glomerular filtration rate, HDU: High dependency unit, IL-6: interleukin-6; ICU: Intensive Care Unit, LDH: lactate dehydrogenase, NVI: Non-invasive ventilation, PCT: procalcitonin, PTH: parathyroid hormone. * Data represented as median (IQR). ** Data represented as mean (CI 95%) 25OHD: 25-hydroyvitamin D, ALT: alanine transaminase, AST: aspartate aminotransferase, BMI: body-mass index, CK: creatine kinase, CRP: C reactive protein, GFR: glomerular filtration rate, HDU: High dependency unit, IL-6: interleukin-6; ICU: Intensive Care Unit, LDH: lactate dehydrogenase, NVI: Non-invasive ventilation, PCT: procalcitonin, PTH: parathyroid hormone. * Data represented as median (IQR). ** Data represented as mean (CI 95%) 25OHD: 25-hydroyvitamin D, ALT: alanine transaminase, AST: aspartate aminotransferase, BMI: body-mass index, CK: creatine kinase, CRP: C reactive protein, GFR: glomerular filtration rate, HDU: High dependency unit, IL-6: interleukin-6; ICU: Intensive Care Unit, LDH: lactate dehydrogenase, NVI: Non-invasive ventilation, PCT: procalcitonin, PTH: parathyroid hormone. * Data represented as median (IQR). ** Data represented as mean (CI 95%) 25OHD: 25-hydroyvitamin D, ALT: alanine transaminase, AST: aspartate aminotransferase, BMI: body-mass index, CK: creatine kinase, CRP: C reactive protein, GFR: glomerular filtration rate, HDU: High dependency unit, IL-6: interleukin-6; ICU: Intensive Care Unit, LDH: lactate dehydrogenase, NVI: Non-invasive ventilation, PCT: procalcitonin, PTH: parathyroid hormone. * Data represented as median (IQR). ** Data represented as mean (CI 95%) 25OHD: 25-hydroyvitamin D, ALT: alanine transaminase, AST: aspartate aminotransferase, BMI: body-mass index, CK: creatine kinase, CRP: C reactive protein, GFR: glomerular filtration rate, HDU: High dependency unit, IL-6: interleukin-6; ICU: Intensive Care Unit, LDH: lactate dehydrogenase, NVI: Non-invasive ventilation, PCT: procalcitonin, PTH: parathyroid hormone. * Data represented as median (IQR). ** Data represented as mean (CI 95%) 25OHD: 25-hydroyvitamin D, ALT: alanine transaminase, AST: aspartate aminotransferase, BMI: body-mass index, CK: creatine kinase, CRP: C reactive protein, GFR: glomerular filtration rate, HDU: High dependency unit, IL-6: interleukin-6; ICU: Intensive Care Unit, LDH: lactate dehydrogenase, NVI: Non-invasive ventilation, PCT: procalcitonin, PTH: parathyroid hormone. * Data represented as median (IQR). ** Data represented as mean (CI 95%) 25OHD: 25-hydroyvitamin D, ALT: alanine transaminase, AST: aspartate aminotransferase, BMI: body-mass index, CK: creatine kinase, CRP: C reactive protein, GFR: glomerular filtration rate, HDU: High dependency unit, IL-6: interleukin-6; ICU: Intensive Care Unit, LDH: lactate dehydrogenase, NVI: Non-invasive ventilation, PCT: procalcitonin, PTH: parathyroid hormone. * Data represented as median (IQR). ** Data represented as mean (CI 95%) 25OHD: 25-hydroyvitamin D, ALT: alanine transaminase, AST: aspartate aminotransferase, BMI: body-mass index, CK: creatine kinase, CRP: C reactive protein, GFR: glomerular filtration rate, HDU: High dependency unit, IL-6: interleukin-6; ICU: Intensive Care Unit, LDH: lactate dehydrogenase, NVI: Non-invasive ventilation, PCT: procalcitonin, PTH: parathyroid hormone. * Data represented as median (IQR). ** Data represented as mean (CI 95%)