Comparison 1. Immunoglobulins versus placebo.

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
1 Mortality (any cause during hospitalisation or follow‐up)	3	196	Risk Ratio (M‐H, Random, 95% CI)	0.87 [0.14, 5.27]
2 Length of hospitalisation (days)	5	324	Mean Difference (IV, Random, 95% CI)	‐0.70 [‐1.83, 0.42]
3 Adverse events of any severity or seriousness	5	340	Risk Ratio (M‐H, Random, 95% CI)	1.18 [0.78, 1.78]
4 Serious adverse events	4	238	Risk Ratio (M‐H, Random, 95% CI)	1.08 [0.65, 1.79]
5 Need for mechanical ventilation	4	341	Risk Ratio (M‐H, Random, 95% CI)	1.24 [0.64, 2.41]
6 Duration of mechanical ventilation	3	100	Mean Difference (IV, Random, 95% CI)	‐0.22 [‐2.64, 2.21]
7 Need for supplemental oxygen	2	142	Risk Ratio (M‐H, Random, 95% CI)	1.18 [0.94, 1.49]
8 Duration of supplemental oxygen	3	115	Mean Difference (IV, Random, 95% CI)	‐0.54 [‐2.26, 1.17]
9 Need for ICU admission	4	341	Risk Ratio (M‐H, Random, 95% CI)	1.22 [0.64, 2.32]
10 Duration of stay in the ICU	2	107	Mean Difference (IV, Random, 95% CI)	‐2.13 [‐4.55, 0.30]