Table 1 Summary of the descriptive characteristics of included studies

Ajayi et al., 2015 [44]

Cross-sectional

Region: SW

State: Lagos

Setting: Urban

Mothers at home in Mushin LGA, Lagos

400

28.1 (9.50)

374 (93.5%)

306 (76.5%)

High

Akinrinde et al., 2018 [45]

Cross-sectional

Region: SW

State: Ondo

Setting: Mixed (Rural, peri-urban, and urban)

Mothers of infants attending routine immunization clinics in 24 randomly selected PHC centers

615

28.5 (6.01)

529 (86.0%)

613 (99.7%)

High

Balogun et al., 2012 [52]

Cross-sectional

Region: SW

State: Lagos

Setting: Urban

Mothers attending the Lagos University Teaching Hospital (LUTH)‘s child welfare clinic, Lagos

399

31.1 (4.70)

391 (98.0%)

308 (77.2%)

High

Bello et al., 2020 [53]

Cross-sectional

Region: NC

State: Nasarawa

Setting: Urban

Mothers of children in the Medical Ward of Dalhatu Araf Specialist Hospital (DASH), Lafia

135

27.5 (5.82)

124 (91.9%)

111 (82.2%)

Low

Brown & Oluwatosin, 2017 [54]

Interventional

Region: SW

State: Oyo

Setting: Urban

Mothers of infants

attending routine immunization clinics in four randomly selected

communities’ PHC centers in Ibadan

595

27.5 (5.82)

590 (99.2%)

584 (98.2%)

High

Brown et al., 2015 [55]

Cross-sectional

Region: SW

State: Oyo

Setting: Urban

Mothers of infants

attending routine immunization clinics in four randomly selected

communities’ PHC centers in Ibadan

614

29.0 (4.90)

607 (98.8%)

584 (95.1%)

High

Dipeolu 2017 [56]

Cross-sectional

Region: SW

State: Oyo

Setting: Rural

Mothers of Infants attending Routine immunization clinics in two randomly selected rural LGAs

366

26.1 (5.55)

366 (100.0%)

340 (92.9%)

High

Eze & Adeleye, 2015 [57]

Interventional

Region: SS

State: Edo

Setting: Urban

Caregivers of infants attending routine immunization from

eight randomly health facilities in Egor LGA in Edo State

905

30.5 (5.43)

896 (99.0%)

843 (93.1%)

High

Eze et al., 2018 [58]

Interventional

Region: SE

State: Ebonyi

Setting: Urban

Caregivers of infants accessing immunization services in rural health facilities in Abakaliki.

290

27.0 (5.21)

290 (100.0%)

285 (98.3%)

Moderate

Ibraheem & Akintola, 2017 [59]

Cross-sectional

Region: NC

State: Kwara

Setting: Urban

Mothers/caregivers bringing their newborns for their first set of vaccines at two public hospitals in Ilorin West LGA

526

28.5 (4.80)

488 (92.8%)

363 (69.0%)

High

Ibraheem et al., 2018 [46]

Cross-sectional

Region: NC

State: Kwara

Setting: Urban

Caregivers bringing their newborns for their first set of vaccines at two public hospitals in Ilorin West LGA

536

28.5 (4.80)

526 (98.1%)

363 (67.7%)

High

Odinaka et al., 2018 [47]

Cross-sectional

Region: SE

State: Imo

Setting: Urban

Mothers of infants attending the immunization clinic of Federal Medical Centre Owerri, Imo State

253

30.4 (7.10)

244 (96.4%)

156 (61.7%)

Moderate

Oladepo et al., 2019 [48]

Cross-sectional

Region: All six regions

States: Abia, Bauchi, Benue, Bayelsa, Katsina, Ondo, and FCT

Setting: Rural

Mothers of infants attending immunization clinics in seven randomly selected states

3500

26.7 (5.50)

3440 (98.3%)

3113 (88.9%)

High

Onoja-Alexander et al., 2018 [49]

Cross-sectional

Region: NW

State: Kaduna

Setting: Urban

Randomly selected caregivers attending routine childhood immunization clinic in ABUTH Shika, Zaria

300

28.7 (4.22)

235 (78.3%)

251 (83.7%)

High

Sadoh & Okungbowa, 2014 [50]

Cross-sectional

Region: SS

State: Edo

Setting: Urban

A conveniently selected sample of mothers of infants attending immunization clinic at the Institute of Child Health, University of Benin, Benin City.

203

30.5 (5.07)

188 (92.6%)

127 (62.6%)

Low

Tagbo et al., 2020 [51]

Cross-sectional

Region: SE

State: Enugu

Setting: Urban

Caregivers bringing their infants for immunization in five randomly selected health facilities in Enugu metropolis

286

29.6 (6.97)

278 (97.2%)

255 (89.2%)

Moderate