Table 1.
Characteristics of the study population according to the peak anti-spike IgG levels post-second vaccination
| Total (n=1635) | Peak antibody levels >700 AU/mL (n=1555) | Peak antibody levels 50–700 AU/mL (n=75) | Peak antibody levels <50 AU/mL (n=5) | Peak antibody levels 14–84 days post-second vaccination (AU/mL) | P value | ||
| Median | IQR | ||||||
| Age (years) | |||||||
| Median | 46 | 46 | 49 | 34 | (Overall) 10 763 | 3925–22 017 | |
| Q1, Q3 | 33, 56 | 33, 56 | 36, 56 | 33, 43 | |||
| Age group | |||||||
| 17–34 | 457 (100.0%) | 439 (96.1%) | 15 (3.3%) | 3 (0.7%) | 14 668 | 5359–25 801 | <0.001 |
| 35–54 | 723 (100.0%) | 682 (94.3%) | 39 (5.4%) | 2 (0.3%) | 10 153 | 3773–20 578 | |
| 55–77 | 455 (100.0%) | 434 (95.4%) | 21 (4.6%) | 0 (0.0%) | 9328 | 3461–19 046 | |
| Sex | |||||||
| Female | 1344 (100.0%) | 1271 (94.6%) | 68 (5.1%) | 5 (0.4%) | 10 779 | 3856–22 541 | 0.7 |
| Male | 290 (100.0%) | 283 (97.6%) | 7 (2.4%) | 0 (0.0%) | 10 710 | 4524–19 026 | |
| Non-disclosed | 1 (100.0%) | 1 (100.0%) | 0 (0.0%) | 0 (0.0%) | 5438 | ||
| Ethnicity | |||||||
| White | 1169 (100.0%) | 1110 (95.0%) | 56 (4.8%) | 3 (0.3%) | 10 971 | 3907–22 009 | 0.3 |
| Asian | 304 (100.0%) | 290 (95.4%) | 14 (4.6%) | 0 (0.0%) | 10 433 | 4180–21 829 | |
| Black | 50 (100.0%) | 45 (90.0%) | 4 (8.0%) | 1 (2.0%) | 7081 | 2104–14 388 | |
| Mixed | 36 (100.0%) | 36 (100.0%) | 0 (0.0%) | 0 (0.0%) | 10 725 | 4573–29 932 | |
| Other | 55 (100.0%) | 53 (96.4%) | 1 (1.8%) | 1 (1.8%) | 8581 | 4703–20 589 | |
| Not stated | 21 (100.0%) | 21 (100.0%) | 0 (0.0%) | 0 (0.0%) | 15 786 | 5686–25 064 | |
| Role | <0.001 | ||||||
| Administrative staff | 245 (100.0%) | 236 (96.3%) | 8 (3.3%) | 1 (0.4%) | 11 653 | 5660–15 013 | |
| Doctor | 106 (100.0%) | 102 (96.2%) | 4 (3.8%) | 0 (0.0%) | 12 003 | 6677–22 113 | |
| Laboratory staff | 61 (100.0%) | 58 (95.1%) | 2 (3.3%) | 1 (1.6%) | 20 279 | 8790–31 137 | |
| Medical or nursing student | 12 (100.0%) | 12 (100.0%) | 0 (0.0%) | 0 (0.0%) | 7933 | 6061–20 103 | |
| Nurse/HCA | 779 (100.0%) | 737 (94.6%) | 39 (5.0%) | 3 (0.4%) | 10 844 | 3897–21 515 | |
| Other | 331 (100.0%) | 314 (94.9%) | 17 (5.1%) | 0 (0.0%) | 9208 | 2533–20 284 | |
| Porter or domestic worker | 31 (100.0%) | 27 (87.1%) | 4 (12.9%) | 0 (0.0%) | 8476 | 1533–15 644 | |
| OT/PT/SLT | 70 (100.0%) | 69 (98.6%) | 1 (1.4%) | 0 (0.0%) | 11 849 | 6021–24 371 | |
| BMI | 0.3 | ||||||
| <16 | 3 (100.0%) | 2 (66.7%) | 1 (33.3%) | 0 (0.0%) | 17 716 | 9195–18 471 | |
| 16–24.9 | 698 (100.0%) | 667 (95.6%) | 28 (4.0%) | 3 (0.4%) | 11 587 | 4186–22 134 | |
| 25–29.9 | 517 (100.0%) | 491 (95.0%) | 24 (4.6%) | 2 (0.4%) | 10 169 | 3404–19 046 | |
| 30–34.9 | 261 (100.0%) | 247 (94.6%) | 14 (5.4%) | 0 (0.0%) | 10 149 | 4318–24 585 | |
| 35–39.9 | 85 (100.0%) | 81 (95.3%) | 4 (4.7%) | 0 (0.0%) | 10 743 | 4534–27 281 | |
| >40 | 71 (100.0%) | 67 (94.4%) | 4 (5.6%) | 0 (0.0%) | 11 199 | 5877–28 260 | |
| Vaccine combination | |||||||
| ChAdOx1/ChAdOx1 | 387 (100.0%) | 315 (81.4%) | 70 (18.1%) | 2 (0.5%) | 1603 | 879–3521 | |
| BNT162b2/BNT162b2 | 1234 (100.0%) | 1227 (99.4%) | 4 (0.3%) | 3 (0.2%) | 14 824 | 8432–25 853 | |
| Other | 13 (100.0%) | 13 (100.0%) | 1 (0.0%) | 0 (0.0%) | 6993 | 4693–13 212 | |
| Evidence of COVID-19 infection at baseline | <0.001 | ||||||
| No | 1349 (100.0%) | 1269 (94.1%) | 75 (5.6%) | 5 (0.4%) | 9960 | 3302–20 056 | |
| Yes | 286 (100.0%) | 286 (100.0%) | 0 (0.0%) | 0 (0.0%) | 17 227 | 7111–28 277 | |
| COVID-age score groups | <0.001 | ||||||
| Low | 769 (100.0%) | 737 (95.8%) | 32 (4.2%) | 0 (0.0%) | 12 337 | 4634–23 170 | |
| Medium | 696 (100.0%) | 659 (94.7%) | 35 (5.0%) | 2 (0.3%) | 9430 | 3693–19 302 | |
| High | 120 (100.0%) | 114 (95.0%) | 5 (4.2%) | 1 (0.8%) | 10 524 | 3106–23 939 | |
| Very high | 22 (100.0%) | 17 (77.3%) | 3 (13.6%) | 2 (9.1%) | 4379 | 889–11 214 | |
| COVID-age score | |||||||
| Median | 50 | 50 | 53 | 76 | |||
| Q1, Q3 | 35, 59 | 35, 60 | 36, 57 | 54, 85 | |||
Other for vaccine included mRNA-1273 and other vaccine combinations.
Bold indicates a significant p value of <0.05.
BMI, body mass index; HCA, healthcare assistant; OT/PT/SLT, occupational therapist, physiotherapist, and speech and language therapist.