Table 1 Characteristics of Studies Included

Al 2021 [18]

United Arab Emirates

Case-control

78 COV, 50 non-COV

Fecal samples

COV: V3-V4;

non-COV: V4

MiSeq

DESeq2

Cervino 2022 [19]

France

Case-control

55 COV, 76 non-COV

Fecal samples

V3-V4

MiSeq

Wilcoxon test

Chen 2022 [26]

China

Longitudinal

26 COV, 20 RP, 30 post-RP, 30 non-COV

Fecal samples

V3-V4

MiSeq

NM

Gaibani 2021 [27]

Italy

Case-control

69 COV, 69 non-COV

Fecal samples

COV: V3-V4;

non-COV: V3-V4, V1-V3

MiSeq,

454 GS Junior

LEfSe

Gu 2020 [28]

China

Case-control

30 COV, 30 non-COV

Fecal samples

V3-V4

MiSeq

LEfSe

Khan 2021 [29]

India

Case-control

30 COV (10 asymptomatic, 10 non-severe, 10 severe), 10 non-COV

Fecal samples

V3-V4

HiSeq 2000

LEfSe

Kim 2021 [30]

Korea

Longitudinal

12 COV, 12 RP, 36 non-COV ^b

Fecal samples

V3–V4

MiSeq

MaAsLin2

Mazzarelli 2021 [31]

Italy

Case-control

15 COV, 8 non-COV

Rectal swabs

V2, V4, V8, V3-6, 7-9

Ion Torrent S5

DESeq2

Moreira-Rosario 2021 [32]

Portugal

Cross-sectional

111 COV (54 non-severe, 57 severe)

Fecal samples

V3-V4

Ion Torrent S5

NM

Newsome 2021 [33]

USA

Case-control

50 COV, 9 RP, 34 non-COV

Fecal samples

V1-V3

MiSeq

edgeR

Rafiqul 2022 [20]

Bangladesh

Case-control

44 COV, 30 non-COV

Fecal samples

V3-V4

MiSeq

Kruskal-Wallis

Reinold 2021 [21]

Germany

Case-control

117 COV (79 non-severe, 38 severe), 95 non-COV

Rectal swabs

V3-V4

NovaSeq 6000

LEfSe

Ren 2021 [22]

China

Case-control

36 COV, 18 RP, 72 non-COV

Fecal samples

V3-V4

MiSeq

LEfSe

Tian 2021 [23]

China

Case-control

7 post-RP, 7 non-COV

Fecal samples

V3-V4

MiSeq

LEfSe

Wu 2021 [24]

China

Case-control

24 COV (21 non-severe, 3 severe; 50 samples), 20 RP (31 samples), 32 non-COV (32 samples)

Fecal samples

V3-V4

NovaSeq 6000

LEfSe/MaAslin2

Zhou 2021 [25]

China

Case-control

15 post-RP, 14 non-COV

Fecal samples

V3-V4

MiSeq

Wilcoxon test