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75 vitamin C COVID-19 controlled studies, 21 RCTs
39% improvement
for early treatment, RR
0.61
[0.47-0.80]
0
0.25
0.5
0.75
1
1.25
1.5
1.75
2+
Su
-135%
2.35 [0.67-8.27]
progression
n/a
n/a
Improvement, RR [CI]
Treatment
Control
Su
-34%
1.34 [1.02-1.73]
no improv.
n/a
n/a
COVIDAtoZ
Thomas (RCT)
-204%
3.04 [0.13-72.9]
death
1/48
0/50
COVIDAtoZ
Thomas (RCT)
31%
0.69 [0.12-3.98]
hosp.
2/48
3/50
COVIDAtoZ
Thomas (RCT)
18%
0.82 [0.63-1.07]
recov. time
48 (n)
50 (n)
Zhao (PSM)
72%
0.28 [0.08-0.93]
progression
4/55
12/55
Zhao (PSM)
-8%
1.08 [0.64-1.80]
viral time
55 (n)
55 (n)
Ried (RCT)
31%
0.69 [0.54-0.89]
no recov.
69/162
46/75
Usanma Koban
33%
0.67 [0.07-5.38]
viral+
31 (n)
95 (n)
Madamombe
53%
0.47 [0.31-0.71]
death
672 (all patients)
Rahman
40%
0.60 [0.47-0.76]
hosp.
128/476
56/124
Krishnan
31%
0.69 [0.47-0.92]
death
40/79
52/73
Zhang (RCT)
50%
0.50 [0.20-1.50]
death
6/27
11/29
ICU patients
Zhang (RCT)
80%
0.20 [0.10-0.90]
death
5/27
11/29
ICU patients
Zhang (RCT)
50%
0.50 [0.20-1.80]
death
6/27
10/29
ICU patients
Zhang (RCT)
70%
0.30 [0.21-1.10]
death
5/27
10/29
ICU patients
Yüksel (ICU)
19%
0.81 [0.66-0.99]
death
31/42
40/44
ICU patients
Patel
29%
0.71 [0.43-1.14]
death
22/96
26/80
Patel
16%
0.84 [0.52-1.36]
death
15/30
16/27
Kumari (RCT)
36%
0.64 [0.26-1.55]
death
7/75
11/75
Kumari (RCT)
20%
0.80 [0.40-1.59]
ventilation
12/75
15/75
Kumari (RCT)
26%
0.74 [0.64-0.86]
recov. time
75 (n)
75 (n)
Kumari (RCT)
24%
0.76 [0.66-0.87]
hosp. time
75 (n)
75 (n)
Darban (RCT)
33%
0.67 [0.14-3.17]
progression
2/10
3/10
ICU patients CT2
Darban (RCT)
6%
0.94 [0.84-1.06]
ICU
10 (n)
10 (n)
ICU patients CT2
Jang
51%
0.49 [0.23-1.01]
no recov.
5/12
6/7
ECMO patients
JamaliMo.. (RCT)
0%
1.00 [0.22-4.56]
death
3/30
3/30
JamaliMo.. (RCT)
-25%
1.25 [0.37-4.21]
ventilation
5/30
4/30
JamaliMo.. (RCT)
-31%
1.31 [1.03-1.66]
hosp. time
30 (n)
30 (n)
Gao
86%
0.14 [0.03-0.72]
death
1/46
5/30
Hamidi-A.. (RCT)
44%
0.56 [0.20-1.51]
death
5/40
9/40
CT2
Hamidi-A.. (RCT)
38%
0.62 [0.45-0.86]
hosp. time
40 (n)
40 (n)
CT2
Al Sulaiman (PSM)
15%
0.85 [0.61-1.12]
death
46/142
59/142
Mulhem
-32%
1.32 [1.07-1.62]
death
157/794
359/2,425
Gadhiya
-1%
1.01 [0.48-1.91]
death
19/55
36/226
Hakamifard (RCT)
46%
0.54 [0.14-2.08]
ICU
3/38
5/34
CT2
Hakamifard (RCT)
1%
0.99 [0.91-1.07]
hosp. time
38 (n)
34 (n)
CT2
Elhadi (ICU)
-12%
1.12 [0.96-1.31]
death
175/277
106/188
ICU patients
Suna
21%
0.79 [0.44-1.41]
death
17/153
24/170
Suna
-2%
1.02 [0.46-2.24]
ICU
11/153
12/170
Pourhoseingholi
13%
0.87 [0.63-1.19]
death
54/199
285/2,269
Li (ICU)
-11%
1.11 [0.79-1.54]
death
7/8
19/24
ICU patients
Vishnuram
54%
0.46 [0.24-0.86]
death
164/8,634
10/241
Özgünay (ICU)
9%
0.91 [0.63-1.30]
death
17/32
75/128
ICU patients
Özgünay (ICU)
-1%
1.01 [0.79-1.29]
ventilation
23/32
91/128
ICU patients
Tan
25%
0.75 [0.10-2.98]
death/int.
1/46
14/115
CT2
Tan
73%
0.27 [0.09-0.61]
ARDS
7/46
41/115
CT2
Zheng (PSM)
-157%
2.57 [0.39-16.8]
death
12/70
7/327
Zheng
-169%
2.69 [0.91-7.89]
death
12/70
7/327
Zheng (PSM)
-35%
1.35 [0.88-2.08]
no improv.
18/70
16/327
Zheng
-32%
1.32 [0.93-1.82]
no improv.
18/70
16/327
Simsek
44%
0.56 [0.23-1.35]
death
6/58
15/81
Simsek
10%
0.90 [0.55-1.46]
ICU
18/58
28/81
Tehrani (RCT)
87%
0.13 [0.01-2.25]
death
0/18
4/26
Tehrani (RCT)
18%
0.82 [0.60-1.13]
hosp. time
18 (n)
26 (n)
Majidi (DB RCT)
14%
0.86 [0.76-0.98]
death
26/31
67/69
ICU patients
Baguma
-48%
1.48 [0.41-4.70]
death
385 (n)
96 (n)
Tu
83%
0.17 [0.08-0.35]
death
8/116
26/64
Yang (RCT)
33%
0.67 [0.55-0.81]
recov. time
10 (n)
10 (n)
CT2
Yang (RCT)
45%
0.55 [0.44-0.71]
recov. time
10 (n)
10 (n)
CT2
Yang (RCT)
24%
0.76 [0.63-0.93]
recov. time
10 (n)
10 (n)
CT2
Yang (RCT)
28%
0.72 [0.58-0.89]
recov. time
10 (n)
10 (n)
CT2
Yang (RCT)
27%
0.73 [0.60-0.89]
recov. time
10 (n)
10 (n)
CT2
Yang (RCT)
23%
0.77 [0.66-0.89]
recov. time
10 (n)
10 (n)
CT2
Yang (RCT)
15%
0.85 [0.68-1.06]
recov. time
10 (n)
10 (n)
CT2
Yang (RCT)
15%
0.85 [0.75-0.97]
recov. time
10 (n)
10 (n)
CT2
Gavrielatou (ICU)
58%
0.42 [0.12-1.48]
death
2/10
49/103
ICU patients
Salehi (ICU)
10%
0.90 [0.65-1.25]
death
22/40
52/85
ICU patients
Coppock (RCT)
5%
0.95 [0.16-7.84]
progression
4/44
2/22
Coppock (RCT)
50%
0.50 [0.16-1.33]
no improv.
6/44
6/22
Coppock (RCT)
22%
0.78 [0.59-1.02]
no disch.
31/44
20/22
Hess (PSW)
20%
0.80 [0.40-1.60]
death
10/25
37/75
Hess (PSW)
40%
0.60 [0.28-1.00]
ventilation
18/25
54/75
Hess (PSW)
50%
0.50 [0.20-0.90]
ventilation
18/25
54/75
Hess (PSW)
27%
0.73 [0.41-1.04]
ICU
22/25
63/75
Hess (PSW)
30%
0.70 [0.40-1.20]
ICU
22/25
63/75
Zangeneh (ICU)
4%
0.96 [0.64-1.45]
death
n/a
n/a
ICU patients
LINCOLN
Izzo
41%
0.59 [0.50-0.69]
recovery
869 (n)
521 (n)
LONG COVID OT1 CT2
LINCOLN
Izzo
68%
0.33 [0.19-0.57]
recovery
869 (n)
521 (n)
LONG COVID OT1 CT2
Fogleman (DB RCT)
4%
0.96 [0.65-1.40]
recovery
32 (n)
34 (n)
Kumar (DB RCT)
23%
0.77 [0.40-1.47]
death
10/30
13/30
ICU patients
Kumar (DB RCT)
21%
0.79 [0.43-1.44]
ventilation
11/30
14/30
ICU patients
Özgülteki̇n (ICU)
-5%
1.05 [0.81-1.36]
death
18/21
18/22
ICU patients
Doocy
63%
0.37 [0.08-1.82]
death
2/64
22/80
Labbani-.. (DB RCT)
33%
0.67 [0.20-2.17]
death
4/37
6/37
Labbani-.. (DB RCT)
-13%
1.13 [0.81-1.58]
hosp. time
37 (n)
37 (n)
Labbani-.. (DB RCT)
16%
0.84 [0.68-1.05]
progression
37 (n)
37 (n)
Labbani-.. (DB RCT)
-9%
1.09 [0.86-1.39]
progression
37 (n)
37 (n)
Labbani-.. (DB RCT)
-6%
1.06 [0.93-1.20]
progression
37 (n)
37 (n)
Labbani-.. (DB RCT)
60%
0.40 [0.14-1.16]
progression
4/37
10/37
Coskun (ICU)
25%
0.75 [0.48-1.15]
death
17/38
24/40
ICU patients
Coskun (ICU)
2%
0.98 [0.76-1.28]
ventilation
28/38
30/40
ICU patients
Coskun (ICU)
28%
0.72 [0.57-0.90]
sofa
38 (n)
40 (n)
ICU patients
Kyagambiddwa
50%
0.50 [0.24-1.04]
death
246 (all patients)
Rana (DB RCT)
55%
0.45 [0.16-1.27]
death
5/139
11/139
ICU patients
Rana (DB RCT)
44%
0.56 [0.19-1.62]
ventilation
5/139
9/139
ICU patients
Rana (DB RCT)
37%
0.63 [0.00-1358]
hosp. time
139 (n)
139 (n)
ICU patients
Mousaviasl (DB RCT)
20%
0.80 [0.32-1.98]
death
8/201
10/200
Mousaviasl (DB RCT)
-99%
1.99 [0.18-21.8]
death
2/201
1/200
Mousaviasl (DB RCT)
-200%
3.00 [0.12-73.1]
ventilation
1/201
0/200
Mousaviasl (DB RCT)
-33%
1.33 [0.47-3.75]
ICU
8/201
6/200
Seely (DB RCT)
48%
0.52 [0.10-2.71]
progression
2/42
4/44
CT2
Seely (DB RCT)
14%
0.86 [0.61-1.22]
no recov.
34 (n)
24 (n)
CT2
Seely (DB RCT)
29%
0.71 [0.28-1.75]
no recov.
7/34
7/24
CT2
Seely (DB RCT)
29%
0.71 [0.31-1.65]
no recov.
32 (n)
31 (n)
CT2
Seely (DB RCT)
14%
0.86 [0.37-1.97]
no recov.
33 (n)
30 (n)
CT2
Seely (DB RCT)
50%
0.50 [0.19-1.34]
no recov.
32 (n)
33 (n)
CT2
Seely (DB RCT)
-12%
1.12 [0.82-1.54]
no recov.
30 (n)
25 (n)
CT2
Seely (DB RCT)
-4%
1.04 [0.77-1.40]
recov. time
34 (n)
24 (n)
CT2
Seely (DB RCT)
12%
0.88 [0.19-4.02]
PASC
3/33
3/29
CT2
Seely (DB RCT)
36%
0.64 [0.16-2.65]
PASC
3/35
4/30
CT2
Seely (DB RCT)
1%
0.99 [0.34-2.93]
PASC
6/35
5/29
CT2
REMAP-CAP
Adhikari (RCT)
-19%
1.19 [0.98-1.46]
death
1,303 (n)
903 (n)
REMAP-CAP
Adhikari (RCT)
-16%
1.16 [0.91-1.47]
death
953 (n)
434 (n)
REMAP-CAP
Adhikari (RCT)
-27%
1.27 [0.92-1.85]
death
350 (n)
469 (n)
REMAP-CAP
Adhikari (RCT)
-35%
1.35 [1.01-1.79]
ventilation
1,032 (n)
528 (n)
REMAP-CAP
Adhikari (RCT)
-69%
1.69 [1.20-2.63]
ventilation
454 (n)
563 (n)
LOVIT-COVID
Adhikari (DB RCT)
28%
0.72 [0.45-1.17]
death
190 (n)
194 (n)
LOVIT-COVID
Adhikari (DB RCT)
28%
0.72 [0.36-1.33]
death
84 (n)
97 (n)
LOVIT-COVID
Adhikari (DB RCT)
28%
0.72 [0.35-1.45]
death
106 (n)
97 (n)
SAFE EVICT CORONA-ALI
Fowler (DB RCT)
19%
0.81 [0.30-2.19]
death
5/22
7/25
ICU patients
SAFE EVICT CORONA-ALI
Fowler (DB RCT)
-2%
1.02 [0.99-1.05]
misc.
21 (n)
23 (n)
ICU patients
Corrao
39%
0.61 [0.23-1.60]
death
9/104
6/42
Corrao
19%
0.81 [0.56-1.12]
death/ICU
104 (n)
42 (n)
Corrao
-102%
2.02 [0.46-8.83]
ICU
10/104
2/42
Corrao
25%
0.75 [0.50-1.12]
hosp. time
104 (n)
42 (n)
Uz
84%
0.16 [0.02-0.97]
death
41 (n)
46 (n)
Uz
90%
0.10 [0.02-0.49]
death
183 (n)
46 (n)
Behera
18%
0.82 [0.45-1.57]
cases
case control
Behera
29%
0.71 [0.40-1.26]
cases
case control
Louca
0%
1.00 [0.97-1.04]
cases
population-based cohort
Mahto
-26%
1.26 [0.63-2.28]
IgG+
34/140
59/549
Bejan
34%
0.66 [0.29-1.53]
death
569 (n)
8,637 (n)
Bejan
25%
0.75 [0.35-1.62]
ventilation
572 (n)
8,657 (n)
Bejan
15%
0.85 [0.43-1.69]
ICU
577 (n)
8,690 (n)
Bejan
0%
1.00 [0.67-1.49]
hosp.
626 (n)
9,122 (n)
COVIDENCE UK
Holt
-3%
1.03 [0.77-1.39]
cases
49/1,580
397/13,647
Abdulateef
19%
0.81 [0.37-1.78]
hosp.
8/132
22/295
Aldwihi
36%
0.64 [0.45-0.86]
hosp.
142/505
95/233
Mohseni
-44%
1.44 [1.22-1.71]
cases
34/43
307/560
Nimer
25%
0.75 [0.54-1.04]
hosp.
52/651
167/1,497
Nimer
17%
0.83 [0.62-1.09]
severe case
66/651
194/1,497
Shehab
4%
0.96 [0.46-1.99]
severe case
14/139
12/114
Loucera
28%
0.72 [0.58-0.88]
death
840 (n)
15,128 (n)
Guldemir
31%
0.69 [0.48-0.99]
hosp.
33/173
84/304
Sharif
46%
0.54 [0.01-0.92]
severe case
n/a
n/a
Sharif
97%
0.03 [0.01-0.22]
severe case
n/a
n/a
Asoudeh
69%
0.31 [0.14-0.65]
severe case
250 (all patients)
Vaisi
38%
0.62 [0.31-1.23]
hosp.
2,818 (n)
1,137 (n)
Vaisi
10%
0.90 [0.69-1.29]
symp. case
2,818 (n)
1,137 (n)
Akbar
14%
0.86 [0.65-1.14]
cases
665 (n)
9,335 (n)
Guan
31%
0.69 [0.50-0.86]
symp. case
28/46
2,017/2,454
Guan
18%
0.82 [0.68-0.94]
symp. case
55/79
2,017/2,454
Guan
7%
0.93 [0.84-1.01]
symp. case
129/167
2,017/2,454
Vitamin C COVID-19 outcomes
c19 early .org
December 2024
1 OT: comparison with other treatment 2 CT: study uses combined treatment
Favors vitamin C
Favors control
Figure S2. Comparison of results for RCTs versus observational studies.
For COVID-19 treatments, there is no significant difference between the results of RCTs and observational studies. Observational studies do not systematically over or underestimate efficacy. For high-cost treatments, there is a non-significant trend towards RCTs showing greater efficacy.
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