Case control study of 201 patients and 201 matched controls in Iran showing vitamin D deficiency associated with COVID-19.
Abdollahi et al., 12/12/2020, retrospective, Iran, Middle East, peer-reviewed, 7 authors.
risk of COVID-19 case, 43.5% lower, RR 0.56, p = 0.001, high D levels 39, low D levels 162, >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.