Table 1.
Healthcare workers with at least one symptomatic study visit between 24 November and 31 December 2021.
| Symptomatic Study Visits 433 |
|||
|---|---|---|---|
| Omicron Infection n = 190 (43.9%) |
NAAT Negative, No Omicron Infection n = 243 238 (56.1%) |
p-Value | |
| Race | 0.68 | ||
| Black-African | 172 (90.5) | 217 (89.3) | |
| Other | 18 (9.5) | 26 (10.7) | |
| Female | 154 (81.5) | 203 (83.5) | 0.58 |
| Mean age in years (SD) | 37.4 (9.2) | 38.0 (10.0) | 0.50 |
| Study site | 0.005 | ||
| CHBAH | 156 (82.) | 185 (76.1) | |
| HJH | 15 (7.9) | 9 (3.7) | |
| CMJAH | 19 (10.0) | 49 (20.2) | |
| No vaccine | 32 (16.8) | 37 (15.2) | 0.72 |
| Ad26.COV.2 single dose a | 121 (63.9) | 149 (61.3) | |
| Ad26.COV.2 booster dose b | 21 (11.1) | 28 (11.5) | |
| BNT162b2 c | 9 (4.7) | 17 (7.0) | |
| Median time in days from 1st Ad26.COV.2 dose to visit (IQR) | 280 (260, 287) | 279 (257, 287) | 0.70 |
| Median time in days from Ad26.COV.2 booster dose to visit (IQR) | 23 (18, 32) | 22 (19, 35) | 0.74 |
| Previously SARS-CoV-2 NAAT-confirmed infection | 53 (27.9) | 101 (41.6) | 0.003 |
| Never infected | 137 (72) | 142 (58.4) | |
| 1st wave d | 32 (16.8) | 48 (19.8) | 0.018 |
| 2nd wave d | 8 (4.2) | 15 (6.2) | |
| 3rd wave d | 13 (6.8) | 36 (14.8) | |
| Previously infected > 1 | 0 | 2 (0.8) | |
| n = 174 e | n = 215 e | ||
| No Ad26.COV.2, no previous SARS-CoV-2 NAAT-confirmed infection | 23 (13.2) | 23 (10.8) | 0.18 |
| No Ad26.COV.2, previous SARS-CoV-2 NAAT-confirmed infection | 9 (5.2) | 14 (6.5) | |
| Ad26.COV.2, no previous SARS-CoV-2 NAAT-confirmed infection | 99 (56.9) | 104 (48.6) | |
| Ad26.COV.2, previous SARS-CoV-2 NAAT-confirmed infection | 43 (24.7) | 73 (34.1) | |
| n = 123 | n = 144 | ||
| Anti-spike IgG binding antibody units > 32/mL | 113 (91.9) | 134 (93.1) | 0.71 |
| Anti-spike IgG geometric mean units (95% CI) | 577 (428, 780) | 968 (755, 1242) | 0.009 |
| Mean time in days from blood collection to visit (SD) | 6.6 (17.8) | 8.2 (19.3) | 0.47 |
| Serology results excluding bloods collected at the time of the current visit | n = 28 | n = 37 | |
| Anti-spike IgG binding antibody units > 32/mL | 25 (89.3) | 35 (94.6) | 0.64 |
| Anti-spike IgG geometric mean units (95% CI) | 511 (312, 836) | 919 (575, 1468) | 0.09 |
| Mean time in days from blood collection to visit (SD) | 29.1 (27.3) | 32.3 (26.1) | 0.64 |
Results are n (%) unless stated otherwise. CHBAH: Chris Hani Baragwanath Academic Hospital; HJH: Helen Joseph Hospital; CMJAH: Charlotte Maxeke Johannesburg Academic Hospital; SD: standard deviation; IQR: interquartile range; CI: confidence interval; NAAT: Nucleic Acid Amplification Test. a Received a single Ad26.COV.2 vaccine dose ≥ 14 days before visit. b Received a booster Ad26.COV.2 vaccine dose ≥ 14 days before visit. c Received two BNT162b2 vaccine doses, with second dose ≥ 14 days before visit. d 1st wave: April to October 2020, 2nd wave: November 2020 to April 2021, 3rd wave: May to September 2021. e Excluding participants who received any BNT162b2 vaccine or those receiving the Ad26.COV.2 vaccine < 14 days before visit.