These two RCT´s makes it seem causal:
https://www.sciencedirect.com/science/article/pii/S0960076020302764
“Effect of calcifediol treatment and best available therapy versus best available therapy on intensive care unit admission and mortality among patients hospitalized for COVID-19: A pilot randomized clinical study”
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Conclusion
Our pilot study demonstrated that administration of a high dose of Calcifediol or 25-hydroxyvitamin D, a main metabolite of vitamin D endocrine system, significantly reduced the need for ICU treatment of patients requiring hospitalization due to proven COVID-19. Calcifediol seems to be able to reduce severity of the disease, but larger trials with groups properly matched will be required to show a definitive answer.
TLDR:
Study with 76 patients used high dose Vitamin-D (21280IU) it massively reduced the risk of needing ICU care (97%) and dying (100%) if admitted to hospital for Covid-19. ICU reduction was statistical significant reduction in death was not.
Vitamin-D group (N:50)
Control Group (N:26)
Statistics.
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Need for ICU was reduced by 97% and was highly statistically significant, P<000.1
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Can also be expressed as 25x reduction
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Death was reduced by 100% but not statistically significant due to insufficient dead people, P=0.11.
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Numbers Needed to treat was 2.
and:
https://pmj.bmj.com/content/early/2020/11/12/postgradmedj-2020-139065
Short term, high-dose vitamin D supplementation for COVID-19 disease: a randomised, placebo-controlled, study (SHADE study)
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Results Forty SARS-CoV-2 RNA positive individuals were randomised to intervention (n=16) or control (n=24) group. Baseline serum 25(OH)D was 8.6 (7.1 to 13.1) and 9.54 (8.1 to 12.5) ng/ml (p=0.730), in the intervention and control group, respectively. 10 out of 16 patients could achieve 25(OH)D>50 ng/ml by day-7 and another two by day-14 [day-14 25(OH)D levels 51.7 (48.9 to 59.5) ng/ml and 15.2 (12.7 to 19.5) ng/ml (p<0.001) in intervention and control group, respectively]. 10 (62.5%) participants in the intervention group and 5 (20.8%) participants in the control arm (p<0.018) became SARS-CoV-2 RNA negative. Fibrinogen levels significantly decreased with cholecalciferol supplementation (intergroup difference 0.70 ng/ml; P=0.007) unlike other inflammatory biomarkers.
Conclusion Greater proportion of vitamin D-deficient individuals with SARS-CoV-2 infection turned SARS-CoV-2 RNA negative with a significant decrease in fibrinogen on high-dose cholecalciferol supplementation.
