Table 3.

COVID-19 Incidence as outcome.

Author [Ref]	Micronutrient in question	Odds Ratio (OR) (95% Confidence Interval); % Population Infected (Infected/Population Size)					Key Findings
		Supplementation		Deficiency
		Supplemented	Non-supplemented	Quintile 1	Quintile 2	Quintile 3
Baktash [20]	Vitamin D						Significantly lower vitamin D levels in the cases ˠ (27.00 nmol/L) compared to non-cases ˠ (52.00 nmol/L, p = 0.0008).
D’Avolio [23]	Vitamin D						Significantly lower 25(OH)D levels in cases (11.1 ng/mL) to non-cases (24.6 ng/mL, p = 0.004). Significant difference in 25(OH)D levels in cases ˠ compared with the 2019 non-cases ˠ (24.6 ng/mL, p < 0.001); but no difference between the 2019 and 2020 non-cases ˠ (p = 0.076).
Fasano [48]	Vitamin D	0.56 (0.32- 0.99) *,a; 4.0% (13/329)	Reference; 8.0% (92/1157) *				44% a lowered odds of incidence when patients reported vitamin D supplementation, compared to non-supplementation (p = 0.048).
Im [25]	Vitamin D3			NR; 12.4% (12/97) #	NR; 32.5% (26/80) #	NR; 52.2% (12/23) #	Significant difference in proportions of cases and controls with deficiency (p = 0.003) and severe deficiency (p = 0.001). Significantly lower mean 25(OH)D levels in cases (15.7 ± 7.9 ng/dL) than in controls (25.0 ± 13.2 ng/dL, p < 0.001).
Mardani [31]	Vitamin D						Significantly lower mean Vitamin D levels in to cases ˠ (18.5 ng/mL) than in non-cases ˠ (30.2 ng/mL, p < 0.0001).
Meltzer [32]	Vitamin D			NR; 12.3% (39/317)	NR; 18.6% (32/172)		No difference in proportion of cases ˠ and non-cases ˠ between non-deficient and deficient groups (p = 0.06).
Merzon [33]	Vitamin D ᶧ			Reference; 69.4% (79/1139) #	1.59 (1.29–2.02); 10.6% (598/5648) #	1.58 (1.13–2.09); 10.3% (105/1020)#	58% to 59% b increase in odds of incidence for the deficient and insufficient group respectively, compared to those with sufficient vitamin D levels. 50% b increase in odds of incidence for the those with low vitamin D levels, compared to those with normal vitamin D levels. Significantly lower mean (±SD) vitamin D levels in cases ˠ (19 ± 8.42 ng/mL) than non-cases ˠ (20.55 ± 9.84 ng/mL, p = 0.026).
	Vitamin D ᶲ			Reference; 69.4% (79/1139)	1.50 (1.13–1.98) b; 10.5% (703/6668) *
Raisi-Estabragh [38]	Vitamin D						No difference in median (±IQR) vitamin D levels, adjusted for seasonality between cases ˠ (33.88 ± 27.01 nmol/L) and non-cases ˠ (35.45 ± 26.78 nmol/L).
Ye [43]	Vitamin D			Reference; 35.6% (36/101) #	3.13 (1.47–6.66); 63.4% (26/41) #		213% increase in odds of incidence for those deficient in Vitamin D, compared to those not deficient. Significant difference in median (IQR) 25(OH)D (nmol/L) levels between cases ˠ (55.6 (41.9–66.1) nmol/L) and healthy controls (71.8 (57.8–83.7) nmol/L, p < 0.05).
Jothimani [26]	Zinc			NR; 33.3% (20/60) #	NR; 84.4% (27/32) #		Significantly lower median (IQR) zinc levels cases ˠ (74.5 (53.4–94.6) mg/dL) compared to controls [105.8 (95.65–120.90) mg/dL, p < 0.001).

* between-group p < 0.05; ^# between group p-value not reported; ˠ cases refer to COVID-19 positive individuals, non-cases refer to COVID-19 negative individuals; ᶧ quintiles classification: sufficiency, insufficiency and deficiency; ᶲ quintiles classification: normal and low; ^a age-adjusted; ^b adjusted for demographic variables, and psychiatric and somatic disorders.