Table 1.
Baseline characteristics of participants in the period when omicron dominated, stratified by rapid antigen test. Values are numbers (percentages) unless stated otherwise
| Characteristics | Flowflex: nasal (n=620); Rotterdam | MPBio; Tilburg | Clinitest; Roosendaal | ||||
|---|---|---|---|---|---|---|---|
| Nasal (n=820) | OP-N (n=543) | Nasal (n=726) | OP-N (n=653) | ||||
| Inclusion dates omicron period (>90% omicron related infections) | 12 Jan-3 Feb | 12-18 Jan | 26 Jan-10 Feb | 12-23 Jan | 25 Jan-8 Feb | ||
| Mean (SD) age (years); range | 37 (14); 16-77 | 38 (14); 16-85 | 36 (13); 16-72 | 39 (14); 16-81 | 40 (13); 16-87 | ||
| Sex, female | 357 (57.6) | 524 (63.9) | 375 (69.1) | 449 (61.8) | 437 (66.9) | ||
| Self-reported reason for testing*: | |||||||
| Positive self-test result | 279 (45.0) | 239 (29.1) | 288 (53.0) | 257 (35.4) | 290 (44.4) | ||
| Symptoms | 405 (65.3) | 510 (62.2) | 354 (65.2) | 459 (63.2) | 390 (59.7) | ||
| Close contact | 72 (11.6) | 170 (20.7) | 58 (10.7) | 144 (19.8) | 99 (15.2) | ||
| Other | 49 (7.9) | 54 (6.6) | 15 (2.8) | 29 (4.0) | 24 (3.7) | ||
| Vaccination status: | |||||||
| Not vaccinated | 75 (12.1) | 68 (8.3) | 56 (10.3) | 90 (12.4) | 66 (10.1) | ||
| Vaccinated with ≥1 dose | 545 (87.9) | 752 (91.7) | 487 (89.7) | 636 (87.6) | 586 (89.7) | ||
| No of doses received†: | |||||||
| 1 | 38 (7.0) | 86 (11.4) | 40 (8.2) | 52 (8.2) | 40 (6.8) | ||
| 2 | 233 (42.8) | 329 (43.8) | 184 (37.8) | 334 (52.5) | 214 (36.5) | ||
| 3 | 274 (50.3) | 336 (44.7) | 263 (54.0) | 248 (39.0) | 332 (56.7) | ||
| Unknown | 0 (0) | 1 (0.1) | 0 (0) | 2 (0.3) | 0 (0) | ||
| Initial vaccination series†: | |||||||
| BNT162b2 (Pfizer-BioNTech) | 438 (80.4) | 502 (66.8) | 341 (70.0) | 410 (64.5) | 352 (60.1) | ||
| mRNA-1273 (Moderna) | 34 (6.2) | 96 (12.8) | 43 (8.8) | 116 (18.2) | 104 (17.7) | ||
| ChAdOx1-S (Oxford-AstraZeneca) | 32 (5.9) | 88 (11.7) | 51 (10.5) | 62 (9.7) | 82 (14.0) | ||
| Ad26.COV2.S (Janssen/Johnson & Johnson) | 40 (7.3) | 62 (8.2) | 50 (10.3) | 45 (7.1) | 44 (7.5) | ||
| Unknown/other | 1 (0.2) | 4 (0.5) | 2 (0.4) | 3 (0.5) | 4 (0.7) | ||
| Booster vaccine†: | |||||||
| Pfizer | 200 (36.7) | 219 (29.1) | 214 (43.9) | 168 (26.4) | 256 (43.7) | ||
| Moderna | 99 (18.2) | 137 (18.2) | 76 (15.6) | 93 (14.6) | 93 (15.9) | ||
| None | 242 (44.4) | 388 (51.6) | 187 (38.4) | 366 (57.5) | 225 (38.4) | ||
| Unknown | 4 (0.7) | 8 (1.1) | 10 (2.1) | 9 (1.4) | 12 (2.0) | ||
| ≥1 previous SARS-CoV-2 infection | 148 (23.9) | 185 (22.6) | 135 (24.9) | 127 (17.5) | 121 (18.5) | ||
| Timing of most recent SARS-CoV-2 infection: | |||||||
| <2 months | 14 (9.5) | 16 (8.6) | 12 (8.9) | 13 (10.2) | 11 (9.1) | ||
| 2-6 months | 24 (16.2) | 22 (11.9) | 25 (18.5) | 7 (5.5) | 34 (28.1) | ||
| 6-12 months | 62 (41.9) | 84 (45.4) | 50 (37.0) | 40 (31.5) | 33 (27.3) | ||
| >12 months | 48 (32.4) | 63 (34.1) | 48 (35.6) | 66 (52.0) | 43 (35.5) | ||
| Unknown | 0 (0) | 0 (0) | 0 (0) | 1 (0.8) | 0 (0) | ||
| Symptom onset: | |||||||
| Day of sampling | 48 (7.7) | 71 (8.7) | 59 (10.9) | 42 (5.8) | 40 (6.1) | ||
| Day before sampling | 239 (38.5) | 281 (34.3) | 179 (33.0) | 201 (27.7) | 178 (27.3) | ||
| 2 days before sampling | 192 (31.0) | 257 (31.3) | 157 (28.9) | 273 (37.6) | 229 (35.1) | ||
| ≥3 days before sampling | 140 (22.6) | 208 (25.4) | 148 (27.3) | 210 (28.9) | 205 (31.4) | ||
| Unknown | 1 (0.2) | 3 (0.4) | 0 (0) | 0 (0) | 1 (0.2) | ||
| Symptoms (self-reported)‡: | |||||||
| Common cold | 543 (87.6) | 717 (87.4) | 499 (91.9) | 613 (84.4) | 583 (89.3) | ||
| Shortness of breath | 93 (15.0) | 109 (13.3) | 87 (16.0) | 99 (13.6) | 102 (15.6) | ||
| Fever | 143 (23.1) | 141 (17.2) | 120 (22.1) | 162 (22.3) | 157 (24.0) | ||
| Coughing | 310 (50.0) | 378 (46.1) | 283 (52.1) | 386 (53.2) | 350 (53.6) | ||
| Loss of taste or smell | 26 (4.2) | 27 (3.3) | 20 (3.7) | 25 (3.4) | 29 (4.4) | ||
| Muscle aches | 137 (22.1) | 154 (18.8) | 122 (22.5) | 192 (26.4) | 152 (23.3) | ||
| Other | 88 (14.2) | 123 (15.0) | 85 (15.7) | 116 (16.0) | 108 (16.5) | ||
| Experience with self-tests: | 589 (95.2) | 791 (96.7) | 535 (98.5) | 698 (96.3) | 627 (96.2) | ||
| Timing of last self-test§: | |||||||
| <7 days | 501 (85.1) | 661 (83.6) | 461 (86.2) | 588 (84.2) | 545 (86.9) | ||
| 1-4 weeks | 64 (10.9) | 92 (11.6) | 51 (9.5) | 75 (10.7) | 47 (7.5) | ||
| >1 months | 23 (3.9) | 37 (4.7) | 22 (4.1) | 35 (5.1) | 34 (5.4) | ||
| Unknown | 1 (0.2) | 1 (0.1) | 9 (0.2) | 0 (0) | 1 (0.2) | ||
| No of ever performed self-tests: | |||||||
| 1-3 | 110 (18.7) | 171 (21.6) | 90 (16.8) | 193 (27.7) | 126 (20.2) | ||
| 4-6 | 125 (21.2) | 198 (25.1) | 128 (23.9) | 208 (29.8) | 182 (29.1) | ||
| 7-10 | 158 (26.8) | 181 (22.9) | 118 (22.1) | 153 (21.9) | 130 (20.8) | ||
| >10 | 196 (33.3) | 240 (30.4) | 199 (37.2) | 144 (20.6) | 187 (29.9) | ||
Flowflex=Flowflex COVID-19 Antigen Home Test (Acon Laboratories); MPBio=Rapid SARS-CoV-2 Antigen Test Card (MP Biomedicals); Clinitest=CLINITEST Rapid COVID-19 Antigen Test (Siemens-Healthineers); OP-N=combined oropharyngeal and nasal; SD=standard deviation.
*
Participants could report more than one reason.
†
Proportion of those vaccinated.
‡
Participants could report more than one symptom. Participants were asked separately whether they had symptoms on the day of study participation. All participants reported symptoms but only 60-65% reported symptoms as a reason for testing.
§
Proportion of those with experience of a self-test.