Retrospective 65 elderly COVID-19 patients and 65 matched controls, showing lower vitamin D levels associated with more severe lung involvement, longer disease duration, and higher mortality. Vitamin D supplementation was less common in the COVID-19 group compared to the control group.
Sulli et al., 2/24/2021, retrospective, Italy, Europe, peer-reviewed, 10 authors, dosage not specified.
risk of COVID-19 case, 50.4% lower, RR 0.50, p < 0.001, treatment 22 of 66 (33.3%), control 43 of 64 (67.2%), vitamin D supplementation.
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.