COVID-19 studies:  C19 studies: C19:  IvermectinIVM Vitamin DV.D HC QHC Q Vitamin CV.C ZincZn PVP-IPVP-I FLVFLV REGNR2 LY-CoVLY RemdesivirRMD
Vitamin D study #58 of 71
1/18 Pre-Exposure Prophylaxis study (treated before exposed to the virus)
Vasheghani et al., Research Square, doi: 10.21203/ (Preprint)
The Association of 25 (OH) Vitamin D Levels and Severity and Outcome of COVID-19: A Cross-sectional Study
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Retrospective 508 hospitalized COVID-19 patients in Iran showing lower mortality with vitamin D supplementation, and an association between low vitamin D levels and disease severity, ICU admission, and increased mortality. Details of supplementation are not provided.

Vasheghani et al., 1/18/2021, retrospective, Iran, Middle East, preprint, 5 authors, dosage not specified.
risk of death, 30.4% lower, RR 0.70, p = 0.45, treatment 7 of 88 (8.0%), control 48 of 420 (11.4%), vitamin D supplementation.
risk of ICU admission, 63.8% lower, RR 0.36, p = 0.009, treatment 13 of 185 (7.0%), control 53 of 323 (16.4%), adjusted per study, vitamin D levels >30ng/mL.

Effect extraction follows pre-specified rules prioritizing more serious outcomes. For an individual study the most serious outcome may have a smaller number of events and lower statistical signficance, however this provides the strongest evidence for the most serious outcomes when combining the results of many trials.
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