Meta analysis of 4 supplementation studies, finding that vitamin D supplementation "seems to decrease the mortality rate, the severity of the disease, and serum levels of the inflammatory markers". Mortality odds ratio OR 0.264,
p = 0.008.
Nikniaz et al., 1/5/2021, preprint, 4 authors.
risk of death, 67.5% lower, RR 0.32, p = 0.008, treatment 13 of 123 (10.6%), control 17 of 67 (25.4%), 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.