Table 1.
Baseline characteristics of eligible participants with the antibody test in the cross-sectional cohort
| First-dose vaccine recipients | Second-dose vaccine recipients | |||||
|---|---|---|---|---|---|---|
| All | Discovery dataset | Validation dataset | All | Discovery dataset | Validation dataset | |
| Number | 107,175 | 97,097 | 10,078 | 67,825 | 61,013 | 6812 |
| Age, mean (SD) | 67.27 (7.59) | 67.23 (7.60) | 67.61 (7.53) | 71.22 (6.56) | 71.21 (6.57) | 71.29 (6.50) |
| Age category, n (%) | ||||||
| 50–59 years | 42,872 (40.0) | 38,671 (39.8) | 4201 (41.7) | 45,931 (67.7) | 41,302 (67.7) | 4629 (68.0) |
| 60–69 years | 19,970 (18.6) | 18,223 (18.8) | 1747 (17.3) | 5085 (7.5) | 4582 (7.5) | 503 (7.4) |
| ≥70 years | 44,333 (41.4) | 40,203 (41.4) | 4130 (41.0) | 16,809 (24.8) | 15,129 (24.8) | 1680 (24.7) |
| Sex, n (%) | ||||||
| Female | 59,761 (55.8) | 54,584 (56.2) | 5177 (51.4) | 39,417 (58.1) | 35,733 (58.6) | 3684 (54.1) |
| Male | 47,414 (44.2) | 42,513 (43.8) | 4901 (48.6) | 28,408 (41.9) | 25,280 (41.4) | 3128 (45.9) |
| Ethnicity | ||||||
| White | 90,511 (84.5) | 81,825 (84.3) | 8686 (86.2) | 56,814 (83.8) | 50,933 (83.5) | 5881 (86.3) |
| Others | 16,664 (15.5) | 15,272 (15.7) | 1392 (13.8) | 11,011 (16.2) | 10,080 (16.5) | 931 (13.7) |
| Weeks since the latest vaccination, n (%) | ||||||
| 1 week | 1677 (1.6) | 1513 (1.6) | 164 (1.6) | 13,222 (19.5) | 11,941 (19.6) | 1281 (18.8) |
| 2 weeks | 2957 (2.8) | 2683 (2.8) | 274 (2.7) | 12,911 (19.0) | 11,624 (19.1) | 1287 (18.9) |
| 3 weeks | 4609 (4.3) | 4173 (4.3) | 436 (4.3) | 10,715 (15.8) | 9675 (15.9) | 1040 (15.3) |
| 4 weeks | 7053 (6.6) | 6408 (6.6) | 645 (6.4) | 8939 (13.2) | 7963 (13.1) | 976 (14.3) |
| 5 weeks | 9188 (8.6) | 8361 (8.6) | 827 (8.2) | 7018 (10.3) | 6295 (10.3) | 723 (10.6) |
| 6 weeks | 10,489 (9.8) | 9558 (9.8) | 931 (9.2) | 4989 (7.4) | 4483 (7.3) | 506 (7.4) |
| 7 weeks | 12,350 (11.5) | 11,171 (11.5) | 1179 (11.7) | 3426 (5.1) | 3068 (5.0) | 358 (5.3) |
| 8 weeks | 14,840 (13.8) | 13,424 (13.8) | 1416 (14.1) | 2438 (3.6) | 2211 (3.6) | 227 (3.3) |
| 9 weeks | 15,613 (14.6) | 14,088 (14.5) | 1525 (15.1) | 1718 (2.5) | 1543 (2.5) | 175 (2.6) |
| 10 weeks | 14,655 (13.7) | 13,263 (13.7) | 1392 (13.8) | 1275 (1.9) | 1153 (1.9) | 122 (1.8) |
| 11 weeks | 11,319 (10.6) | 10,272 (10.6) | 1047 (10.4) | 733 (1.1) | 650 (1.1) | 83 (1.2) |
| 12 weeks | 2425 (2.3) | 2183 (2.2) | 242 (2.4) | 441 (0.7) | 407 (0.7) | 34 (0.5) |
| Vaccine types, n (%)a | ||||||
| ChAdOx1 | 39,948 (37.3) | 36,366 (37.5) | 3582 (35.5) | 18,578 (27.4) | 16,721 (27.4) | 1857 (27.3) |
| BNT162b2 | 15,188 (14.2) | 13,690 (14.1) | 1498 (14.9) | 17,587 (25.9) | 15,886 (26.0) | 1701 (25.0) |
| Unknown | 52,039 (48.6) | 47,041 (48.4) | 4998 (49.6) | 31,660 (46.7) | 28,406 (46.6) | 3254 (47.8) |
aCalculated based on a subgroup of participants who had complete linkage to primary care records for information on COVID-19 vaccine types.