Case control study with 191 COVID-19 patients and 203 healthy controls in Iran, showing an association between vitamin D deficiency and COVID-19 infection and severity. 84.4% of COVID-19 patients had vitamin D deficiency.
Matin et al., 7/30/2021, retrospective, case control, Iran, Middle East, peer-reviewed, 8 authors.
risk of COVID-19 case, 66.1% lower, RR 0.34, p < 0.001, >20ng/mL, RR approximated with OR.
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.