Comparison 2. Subgroup analysis (vitamin D baseline status): Vitamin D supplementation vs. placebo or standard care alone in individuals with moderate to severe disease.

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
2.1 All‐cause mortality	1		Risk Ratio (M‐H, Random, 95% CI)	Subtotals only
2.1.1 Vitamin D non‐deficient	1	122	Risk Ratio (M‐H, Random, 95% CI)	0.97 [0.30, 3.17]
2.1.2 Vitamin D deficient	1	115	Risk Ratio (M‐H, Random, 95% CI)	4.07 [0.47, 35.31]
2.2 Need for mechanical ventilation	1		Risk Ratio (M‐H, Random, 95% CI)	Subtotals only
2.2.1 Vitamin D non‐deficient	1	122	Risk Ratio (M‐H, Random, 95% CI)	0.40 [0.15, 1.08]
2.2.2 Vitamin D deficient	1	115	Risk Ratio (M‐H, Random, 95% CI)	0.81 [0.23, 2.88]
2.3 Admission to intensive care unit	1		Risk Ratio (M‐H, Random, 95% CI)	Subtotals only
2.3.1 Vitamin D non‐deficient	1	122	Risk Ratio (M‐H, Random, 95% CI)	1.29 [0.48, 3.50]
2.3.2 Vitamin D deficient	1	115	Risk Ratio (M‐H, Random, 95% CI)	1.24 [0.56, 2.77]