Table 1.
Characteristics of study participants (n=19 622). Data are number (%)
| Characteristic | Unvaccinated (n=4686) | Vaccinated (n=14 936) | Overall (n=19 622) |
| Age (years):* | |||
| 18-24 | 907 (19.36) | 1461 (9.78) | 2368 (12.07) |
| 25-29 | 1624 (34.66) | 5179 (34.67) | 6803 (34.67) |
| 30-34 | 1311 (27.98) | 5231 (35.02) | 6542 (33.34) |
| 35-39 | 615 (13.12) | 2247 (15.04) | 2862 (14.59) |
| 40-45 | 229 (4.89) | 818 (5.48) | 1047 (5.34) |
| Race or ethnic group: | |||
| Asian | 20 (0.43) | 130 (0.87) | 150 (0.76) |
| Black | 170 (3.63) | 346 (2.32) | 516 (2.63) |
| Hispanic | 76 (1.62) | 235 (1.57) | 311 (1.58) |
| Middle Eastern or North African | 15 (0.32) | 41 (0.27) | 56 (0.29) |
| Native Hawaiian or Pacific Islander | 4 (0.09) | 19 (0.13) | 23 (0.12) |
| White | 1513 (32.29) | 5306 (35.52) | 6819 (34.75) |
| No data | 2888 (61.63) | 8859 (59.32) | 11 747 (59.86) |
| Parity: | |||
| Nulliparous | 3192 (68.12) | 11 509 (77.06) | 14 701 (74.92) |
| Parous | 757 (16.15) | 1885 (12.62) | 2642 (13.46) |
| No data | 737 (15.73) | 1542 (10.32) | 2279 (11.61) |
| Body mass index:† | |||
| Underweight | 144 (3.07) | 428 (2.87) | 572 (2.92) |
| Normal weight | 2057 (43.90) | 7274 (48.70) | 9331 (47.55) |
| Overweight | 564 (12.04) | 1924 (12.88) | 2488 (12.68) |
| Obese | 233 (4.97) | 852 (5.70) | 1085 (5.53) |
| No data | 1688 (36.02) | 4458 (29.85) | 6146 (31.32) |
| Education level: | |||
| Less than undergraduate degree | 1215 (25.93) | 2205 (14.76) | 3420 (17.43) |
| Undergraduate degree or more | 2496 (53.27) | 10 540 (70.57) | 13 036 (66.44) |
| No data | 975 (20.81) | 2191 (14.67) | 3166 (16.13) |
| Relationship status: | |||
| Not in relationship | 631 (13.47) | 1928 (12.91) | 2559 (13.04) |
| In relationship | 3002 (64.06) | 10 553 (70.65) | 13 555 (69.08) |
| No data | 1053 (22.47) | 2455 (16.44) | 3508 (17.88) |
| Geographical region: | |||
| UK or Channel Islands | 1098 (23.43) | 5124 (34.31) | 6222 (31.71) |
| Europe‡ | 1151 (24.56) | 5433 (36.38) | 6584 (33.55) |
| US or Canada | 2002 (42.72) | 3608 (24.16) | 5610 (28.59) |
| Australia or New Zealand | 377 (8.05) | 390 (2.61) | 767 (3.91) |
| Other§ | 58 (1.24) | 381 (2.55) | 439 (2.24) |
| Vaccine type: | |||
| Not vaccinated | 4686 (100.00) | 0 (0.00) | 4686 (23.88) |
| Oxford-AstraZeneca | – | 1353 (9.06) | 1353 (6.90) |
| Covaxin | – | 3 (0.02) | 3 (0.02) |
| Covishield | – | 2 (0.01) | 2 (0.01) |
| Johnson & Johnson | – | 283 (1.89) | 283 (1.44) |
| Moderna | – | 2608 (17.46) | 2608 (13.29) |
| Pfizer-BioNTech | – | 9929 (66.48) | 9929 (50.60) |
| Sinopharm | – | 14 (0.09) | 14 (0.07) |
| Sinovac | – | 60 (0.40) | 60 (0.31) |
| Sputnik | – | 5 (0.03) | 5 (0.03) |
| Unspecified | – | 679 (4.55) | 679 (3.46) |
All characteristics were P<0.001 except vaccine type, in which no statistical test was performed. P values represent comparisons by vaccination group using Pearson’s χ2 test.
*At start of cycle 1.
†At enrolment into application.
‡56% based in Sweden (not including the UK).
§62% based in Brazil.