Retrospective database analysis showing patients with vitamin D deficiency were 4.6 times more likely to be COVID-19 positive, p
Katz et al., 12/4/2020, retrospective, population-based cohort, USA, North America, peer-reviewed, 3 authors.
risk of COVID-19 case, 78.4% lower, RR 0.22, p < 0.001, adjusted per study.
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.