Table 4.
Factors associated with SARS-CoV-2 antibody detection using two methods of detection in Johannesburg, South Africa, March-June 2021: (i) EITHER Wantai or Roche assay detection; and (ii) BOTH Wantai and Roche assay detection.
| Antibodies detected on EITHER Wantai or Roche Assay |
Antibodies detected on BOTH Wantai and Roche Assays |
|||
|---|---|---|---|---|
| Characteristics | SARS-CoV-2 antibodies detected n/N (%) | Unadjusted prevalence ratiosb (95% CI) | SARS-CoV-2 antibody detected n/N (%) | Unadjusted prevalence ratiosb (95% CI) |
| Overall | 320/500 (64.0) | - | 270/500 (54.0) | - |
| Month of enrollment | ||||
| March 2021 | 68/110 (61.8) | Reference | 61/110 (55.5) | Reference |
| April 2021 | 112/170 (65.9) | 1.07 (0.79-1.44) | 92/170 (54.1) | 0.98 (0.71-1.34) |
| May 2021 | 114/177 (64.4) | 1.04 (0.77-1.41) | 92/177 (52.0) | 0.94 (0.68-1.29) |
| June 2021 | 26/43 (60.5) | 0.98 (0.62-1.54) | 25/43 (58.1) | 1.05 (0.66-1.67) |
| Median age (IQR) in years | 27.46 (23.42-31.63) | 0.99 (0.98-1.01) | 27.69 (23.35-31.97) | 0.99 (0.98-1.02) |
| Age group | ||||
| 15-19 | 17/27 (63.0) | 0.99 (0.59-1.66) | 16/27 (59.3) | 1.11 (0.65-1.90) |
| 20-24 | 94/148 (63.5) | Reference | 79/148 (53.4) | Reference |
| 25-29 | 101/150 (67.3) | 1.06 (0.80-1.40) | 81/150 (54.0) | 1.01 (0.74-1.38) |
| 30-34 | 65/106 (61.3) | 0.97 (0.70-1.32) | 54/106 (50.9) | 0.95 (0.66-1.35) |
| 35-39 | 38/58 (65.5) | 1.03 (0.71-1.50) | 35/58 (60.3) | 1.13 (0.76-1.68) |
| ≥40 | 5/11 (45.5) | 0.72 (0.29-1.76)a | 5/11 (45.5) | 0.85 (0.34-2.10) |
| Clinic/Site | ||||
| Esselen Street Clinic | 149/250 (59.6) | Reference | 126/250 (50.4) | Reference |
| Shandukani Midwife Obstetric Unit | 171/250 (68.4) | 1.15 (0.92-1.43)a | 144/250 (57.6) | 1.14 (0.90-1.45) |
| Nationality | ||||
| South African | 157/253 (62.1) | Reference | 134/253 (52.9) | Reference |
| Zimbabwean | 152/231 (65.8) | 1.06 (0.85-1.33) | 126/231 (54.6) | 1.03 (0.81-1.31) |
| Other | 11/16 (68.8) | 1.11 (0.60-2.04) | 10/16 (62.5) | 1.18 (0.62-2.24) |
| Parity | ||||
| 0 | 118/182 (64.8) | Reference | 104/182 (57.2) | Reference |
| 1 | 113/176 (64.2) | 0.99 (0.63-1.50) | 92/176 (52.3) | 0.91 (0.69-1.21) |
| 2-4 | 87/135 (64.4) | 0.99 (0.62-1.57) | 73/135 (54.1) | 0.95 (0.70-1.27) |
| ≥ 5 | 1/1 (100) | 1.54 (0.22-11.04) | 1/1 (100) | 1.75 (0.24-12.54) |
| Gravidity | ||||
| 1 | 99/156 (63.5) | Reference | 85/156 (54.5) | Reference |
| 2-4 | 208/320 (65.0) | 1.02 (0.81-1.30) | 175/320 (54.7) | 1.00 (0.77-1.30) |
| ≥ 5 | 12/18 (66.7) | 1.05 (0.58-1.91) | 10/18 (55.6) | 1.02 (0.53-1.96) |
| Median gestational age of fetus (IQR) (weeks) | ||||
| 27 (21-34) | 0.99 (0.98-1.01) | 27 (21-34) | 0.99 (0.98-1.01) | |
| Trimester of pregnancy | ||||
| First trimester | 7/12 (58.3) | 0.91 (0.43-1.95) | 5/12 (41.67) | 0.77 (0.32-1.89) |
| Second trimester | 147/223 (65.9) | 1.03 (0.83-1.29) | 126/223 (56.5) | 1.05 (0.83-1.34) |
| Third trimester | 165/259 (63.7) | Reference | 139/259 (53.7) | Reference |
| HIV status | ||||
| Negative | 238/360 (66.1) | Reference | 204/360 (56.7) | Reference |
| Positive | 76/131 (58.0) | 0.88 (0.68-1.14) | 61/131 (46.6) | 0.82 (0.62-1.09)a |
| HIV viral load (copies/ml) | ||||
| <100 | 36/69 (52.2) | Reference | 32/69 (46.4) | Reference |
| ≥100 | 7/12 (58.3) | 1.11 (0.50-2.51) | 5/12 (41.7) | 0.90 (0.35-2.31) |
| Clusters of differentiation 4+ T cells (count/ml) | ||||
| ≥350 | 24/39 (61.5) | Reference | 21/39 (53.85) | Reference |
| <350 | 7/18 (38.9) | 0.63 (0.27-1.47) | 4/18 (22.2) | 0.41 (0.14-1.20)a |
| Syphilis | ||||
| Negative | 285/444 (64.2) | Reference | 241/444 (54.3) | Reference |
| Positive | 10/17 (58.8) | 0.92 (0.49-1.72) | 9/17 (52.9) | 0.98 (0.50-1.90) |
| Symptoms suggestive of any previous COVID infection (since March 2020) | ||||
| Yes | 11/19 (57.9) | 0.90 (0.49-1.64) | 10/19 (54.1) | 0.98 (0.52-1.83) |
| No | 309/481 (64.2) | Reference | 260/481 (52.6) | Reference |
| Prior positive COVID test | ||||
| Yes | 6/6 (100.0) | 1.57 (0.70-3.53) | 6/6 (100.0) | 1.87 (0.83-4.20)a |
| No | 314/494 (63.6) | Reference | 264/494 (53.4) | Reference |
| Willing to take COVID-19 vaccine when available | ||||
| Yes | 182/296 (61.5) | Reference | 157/296 (55.5) | Reference |
| No/Unsure | 136/202 (67.3) | 1.09 (0.88-1.37) | 112/202 (55.5) | 1.04 (0.82-1.33) |
a
P-values <0.25 on univariate regression
b
Multivariable logistic regression results not shown. None of the candidate variables from the univariate regression became significant predictors of the outcome when assessed together in a multivariable model.
CI, confidence interval; IQR, interquartile range