Table 5 Meta-regression analysis of factors associated with VE against SARS-CoV-2 infection

Study region^b

 Western Pacific Region

Ref

–

–

–

1

–

 Region of Americas

 − 0.110

(− 0.540, 0.320)

0.610

0.214

0.896

(0.583, 1.377)

 European region

 − 0.002

(− 0.494, 0.490)

0.993

0.245

0.998

(0.610, 1.632)

 Region of South-East Asia

 − 0.041

(− 0.673, 0.592)

0.898

0.315

0.960

(0.510, 1.808)

 Eastern Mediterranean region

 − 0.828

(− 1.480, − 0.175)

0.014

0.325

0.437

(0.228, 0.839)

VOC

 Alpha

Ref

–

–

–

1

–

 Gamma

0.759

(− 0.210, 1.727)

0.122

0.483

2.136

(0.811, 5.626)

 Delta

0.413

(− 0.417, 1.244)

0.323

0.414

1.512

(0.659, 3.469)

 Omicron

1.086

(0.169, 2.004)

0.021

0.457

2.963

(1.184, 7.416)

 Others^c

0.543

(− 0.364, 1.451)

0.235

0.453

1.722

(0.695, 4.269)

Time since vaccination

 14–90

Ref

–

–

–

1

–

 91–180

0.533

(− 0.039, 1.106)

0.067

0.176

1.704

(0.961, 3.021)

  > 180

0.572

(0.085, 1.059)

0.022

0.285

1.772

(1.089, 2.885)

 Others^d

0.158

(− 0.194, 0.510)

0.372

0.243

1.171

(0.824, 1.666)

 Constant

 − 1.370

(− 2.258, − 0.481)

0.003

0.443

0.254

(0.105, 0.618)