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 meta
2017 N/A
Martineau et al., BMJ 2017, 356, doi:10.1136/bmj.i6583 (Peer Reviewed) (meta analysis)
Vitamin D supplementation to prevent acute respiratory tract infections: systematic review and meta-analysis of individual participant data
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Meta analysis of 25 RCTs showing vitamin D supplementation was safe and it protected against acute respiratory tract infection overall. Patients who were very vitamin D deficient and those not receiving bolus doses experienced the most benefit.
Vitamin D supplementation reduced the risk of acute respiratory tract infection among all participants (adjusted odds ratio aOR 0.88 [0.81-0.96], p=0.003.
In subgroup analysis, protective effects were seen in those receiving daily or weekly vitamin D without additional bolus doses (aOR 0.81 [0.72-0.91]) but not in those receiving one or more bolus doses (aOR 0.97 [0.86-1.10]). Among those receiving daily or weekly vitamin D, protective effects were stronger in those with baseline 25-hydroxyvitamin D levels <25 nmol/L (aOR 0.30 [0.17-0.53]) than in those with baseline 25-hydroxyvitamin D levels ≥25 nmol/L (aOR 0.75 [0.60-0.95]).

Martineau et al., 1/1/2017, peer-reviewed, 25 authors.
risk of COVID-19 case, 7.3% lower, RR 0.93, p = 0.003, odds ratio converted to relative risk.

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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