Table 1 Key characteristics of vaccinated and control groups included in the vaccination and miscarriage analyses
Cohort characteristics | Vaccinated | Unvaccinated (historical) | Unvaccinated (contemporary) | |
|---|---|---|---|---|
Number of pregnancies | 18,780 | 56,340 | 18,780 | |
Median age (min–max) | 31 (14–51) | 31 (14–51) | 31 (14–54) | |
Deprivation (SIMD quintile) | 1 (most deprived) | 3501 (18.6%) | 12,258 (21.8%) | 4406 (23.5%) |
2 | 3503 (18.7%) | 11,031 (19.6%) | 3803 (20.3%) | |
3 | 3509 (18.7%) | 10,018 (17.8%) | 3457 (18.4%) | |
4 | 4171 (22.2%) | 11,657 (20.7%) | 3743 (19.9%) | |
5 (least deprived) | 3952 (21.0%) | 10,807 (19.2%) | 3241 (17.3%) | |
Unknown | 144 (0.8%) | 569 (1.0%) | 130 (0.7%) | |
Ethnicity | White | 15,897 (84.6%) | 37,156 (65.9%) | 15,672 (83.5%) |
South Asian | 708 (3.8%) | 1274 (2.3%) | 633 (3.4%) | |
Black/Caribbean/African | 234 (1.2%) | 676 (1.2%) | 375 (2.0%) | |
Other/mixed ethnicity | 596 (3.2%) | 1410 (2.5%) | 683 (3.6%) | |
Unknown | 1345 (7.2%) | 15,824 (28.1%) | 1417 (7.5%) | |
Urban/rural status | Large urban areas | 6801 (36.2%) | 21,263 (37.7%) | 6999 (37.3%) |
Other urban areas | 5974 (31.8%) | 20,171 (35.8%) | 6561 (34.9%) | |
Accessible small towns | 1439 (7.7%) | 4512 (8.0%) | 1390 (7.4%) | |
Remote small towns | 550 (2.9%) | 1597 (2.8%) | 572 (3.0%) | |
Accessible rural areas | 1984 (10.6%) | 5611 (10.0%) | 2088 (11.1%) | |
Remote rural areas | 831 (4.4%) | 2532 (4.5%) | 767 (4.1%) | |
Unknown | 1201 (6.4%) | 654 (1.2%) | 403 (2.1%) | |
Clinical vulnerability | Extremely vulnerable | 228 (1.2%) | 769 (1.4%) | 154 (0.8%) |
Vulnerable | 4819 (25.7%) | 15,917 (28.3%) | 4868 (25.9%) | |
Not vulnerable | 13,733 (73.1%) | 39,654 (70.4%) | 13,758 (73.3%) | |
Exposure (vaccination) | ||||
Gestation at first vaccination | Preconception | 8816 (46.9%) | – | – |
2 + 0–5 + 6 weeks | 4173 (22.2%) | – | – | |
6 + 0–10 + 6 weeks | 1311 (7.0%) | – | – | |
11 + 0–15 + 6 weeks | 2468 (13.1%) | – | – | |
16 + 0–19 + 6 weeks | 2012 (10.7%) | – | – | |
Number of vaccinationsa | 1 | 13,792 (73.4%) | – | – |
2+ | 4988 (26.6%) | – | – | |
Dose number at first vaccination | Dose 1 | 10,974 (58.4%) | – | – |
Dose 2 | 6052 (32.2%) | – | – | |
Dose 3 | 1754 (9.3%) | – | – | |
Type of vaccinationa | BNT162b2 | 13,675 (72.8%) | – | – |
mRNA-1273 | 2260 (12.0%) | – | – | |
ChAdOx1-S/nCoV-19 | 2612 (13.9%) | – | – | |
1+ different type | 233 (1.2%) | – | – | |
Outcome (miscarriage) | ||||
Number of miscarriages ≤ 19 + 6 weeks | 1716 | 5566 | 1878 | |
Gestation at miscarriage | ≤10 + 6 | 1302 (75.9%) | 5113 (91.9%) | 1313 (69.9%) |
11 + 0–13 + 6 | 300 (17.5%) | 295 (5.3%) | 412 (21.9%) | |
≥14 + 0 | 114 (6.6%) | 158 (2.8%) | 153 (8.1%) | |
Imputed gestation for miscarriage | Yes | 975 (56.8%) | 4593 (82.5%) | 927 (49.4%) |
No—from ANC booking | 576 (33.6%) | 308 (5.5%) | 721 (38.4%) | |
No—from end of pregnancy record | 165 (9.6%) | 665 (11.9%) | 230 (12.2%) | |
Interval to miscarriageb | <2 weeks | 84 (4.9%) | 223 (4.0%) | 101 (5.4%) |
2–5 weeks | 258 (15.0%) | 657 (11.8%) | 262 (14.0%) | |
6–9 weeks | 536 (31.2%) | 1902 (34.2%) | 586 (31.2%) | |
≥10 weeks | 838 (48.8%) | 2784 (50.0%) | 929 (49.5%) |
