Table 1.

Study characteristics of all included studies (N = 6).

S. No.	Author and Year	Study design	Study Setting	Duration	Disease severity	Sample Size (I/C)	Mean Age	Gender	Mode of administration	Dose of Vitamin-C	Intervention duration	Total cumulative dose of Vitamin-C
1	Zhang J et al., 2021 [14]	Multicenter, randomized trial	ICUs of 3 hospitals in Hubei, China Taihe Hospital	14th February 14, 2020 to 29th March 2020	Severe	56 (27/29)	66.7 ± 12.7	Males: 66.1%	Central vein catheterization controlled by a pump (IV)	24g/day	7 days	168g
2	Kumari P et al., 2020 [15]	Prospective, open-label RCT	A tertiary care hospital in Karachi, Pakistan	March to July 2020	Severe	150 (75/75)	I = 52 + 11; C = 53 + 12	Males = 56.9%; Females = 43.1%	Intravenous	50 mg/kg/day	Same as length of stay	24g (∼)
3	Siahkali S et al., 2021 [19]	Open-label, non-blinded, randomized controlled trial	Ziaeian Hospital, Tehran, Iran	April and May 2020	Severe	60 (30/30)	C = 57.53 + 18.27; I = 61 + 15.90	M = 50%; F = 50%	Intravenous	6g/day	5 days	30g
4	Hakamifard A et al., 2021 [18]	Randomized controlled clinical trial	Amin hospital of Isfahan, Iran, affiliated to Isfahan University of Medical Sciences	March to April 2020	Non-severe	72 (38/34)	I = 35.68; C = 37.41	M = 63.9%; F = 36.1%	Oral	1g/day
5	Darban M et al., 2021 [17]	Pilot single-center randomized, controlled, open-label, parallel-group trial	Kowsar Hospital, Semnan, Iran		Severe	20 (10/10)	59 ± 19	M = 65%; F = 35%	Intravenous	8g/day	10 days
6	Thomas S et al., 2021 [16]	Multicenter, single health system factorial randomized open-label trial	Outpatient care in sites in Ohio and Florida	April 27, 2020, to October 14, 2020	Non-severe	214 (ASC vs. ST 48/50; ASC + Zn vs. Zn 58/58)	I = 47.15 + 14.65 (45.6 + 15 and 48.7 + 14.3); C = 42 + 14.6	I = 64/106 female and 42/106 males; C = 31/50 female and 19/50 males	Oral	8000 mg of ascorbic acid (to be divided over 2–3 times per day with meals)	10 days

Abbreviation: ASC = Ascorbic acid; ST=Standard.