Table 1.
Baseline characteristics of the eligible and matched primary-infection and infection-naïve cohorts in the Pre-Omicron Reinfection Study and the Omicron Reinfection Study
| Characteristics | Pre-Omicron Reinfection Study | Omicron Reinfection Study | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Full eligible cohorts | Matched cohortsa | Full eligible cohorts | Matched cohortsa | |||||||||
| Primary-infection cohort |
Infection- naïve cohort |
SMDb | Primary-infection cohort |
Infection- naïve cohort |
SMDb | Primary-infection cohort | Infection- naïve cohort |
SMDb | Primary-infection cohort | Infection- naïve cohort |
SMDb | |
| N = 301 943 | N = 2 329 039 | N = 290 638 | N = 290 638 | N = 127 075 | N = 2 329 039 | N = 120 483 | N = 120 483 | |||||
| Median age (IQR)—years | 32 (24–40) | 31 (24–39) | 0.05c | 32 (24–40) | 32 (24–40) | 0.00c | 27 (9–36) | 31 (24–39) | 0.36c | 27 (9–36) | 27 (9–36) | 0.00c |
| Age group | ||||||||||||
| 0–9 years | 29 583 (9.8) | 258 890 (11.1) | 0.07 | 29 022 (10.0) | 29 022 (10.0) | 0.00 | 32 465 (25.6) | 258 890 (11.1) | 0.40 | 31 834 (26.4) | 31 834 (26.4) | 0.00 |
| 10–19 years | 22 830 (7.6) | 168 154 (7.2) | 21 900 (7.5) | 21 900 (7.5) | 11 338 (8.9) | 168 154 (7.2) | 10 630 (8.8) | 10 630 (8.8) | ||||
| 20–29 years | 71 904 (23.8) | 585 421 (25.1) | 70 011 (24.1) | 70 011 (24.1) | 27 556 (21.7) | 585 421 (25.1) | 26 467 (22.0) | 26 467 (22.0) | ||||
| 30–39 years | 96 468 (32.0) | 736 856 (31.6) | 93 754 (32.3) | 93 754 (32.3) | 32 736 (25.8) | 736 856 (31.6) | 31 340 (26.0) | 31 340 (26.0) | ||||
| 40–49 years | 52 822 (17.5) | 363 820 (15.6) | 50 356 (17.3) | 50 356 (17.3) | 15 008 (11.8) | 363 820 (15.6) | 13 908 (11.5) | 13 908 (11.5) | ||||
| 50–59 years | 20 772 (6.9) | 151 131 (6.5) | 19 234 (6.6) | 19 234 (6.6) | 5453 (4.3) | 151 131 (6.5) | 4597 (3.8) | 4597 (3.8) | ||||
| 60–69 years | 5950 (2.0) | 50 033 (2.2) | 5127 (1.8) | 5127 (1.8) | 1937 (1.5) | 50 033 (2.2) | 1376 (1.1) | 1376 (1.1) | ||||
| 70+ years | 1614 (0.5) | 14 734 (0.6) | 1234 (0.4) | 1234 (0.4) | 582 (0.5) | 14 734 (0.6) | 331 (0.3) | 331 (0.3) | ||||
| Sex | ||||||||||||
| Male | 220 978 (73.2) | 1 625 533 (69.8) | 0.08 | 212 685 (73.2) | 212 685 (73.2) | 0.00 | 85 134 (67.0) | 1 625 533 (69.8) | 0.06 | 80 791 (67.1) | 80 791 (67.1) | 0.00 |
| Female | 80 965 (26.8) | 703 506 (30.2) | 77 953 (26.8) | 77 953 (26.8) | 41 941 (33.0) | 703 506 (30.2) | 39 692 (32.9) | 39 692 (32.9) | ||||
| Nationalityd | ||||||||||||
| Bangladeshi | 26 984 (8.9) | 152 627 (6.6) | 0.24 | 25 217 (8.7) | 25 217 (8.7) | 0.00 | 5808 (4.6) | 152 627 (6.6) | 0.19 | 5280 (4.4) | 5280 (4.4) | 0.00 |
| Egyptian | 15 517 (5.1) | 121 086 (5.2) | 15 275 (5.3) | 15 275 (5.3) | 7789 (6.1) | 121 086 (5.2) | 7525 (6.3) | 7525 (6.3) | ||||
| Filipino | 23 569 (7.8) | 169 647 (7.3) | 23 252 (8.0) | 23 252 (8.0) | 9244 (7.3) | 169 647 (7.3) | 9070 (7.5) | 9070 (7.5) | ||||
| Indian | 80 738 (26.7) | 641 424 (27.5) | 80 426 (27.7) | 80 426 (27.7) | 33 697 (26.5) | 641 424 (27.5) | 33 122 (27.5) | 33 122 (27.5) | ||||
| Nepalese | 36 149 (12.0) | 201 681 (8.7) | 33 226 (11.4) | 33 226 (11.4) | 11 459 (9.0) | 201 681 (8.7) | 10 373 (8.6) | 10 373 (8.6) | ||||
| Pakistani | 16 779 (5.6) | 126 346 (5.4) | 16 182 (5.6) | 16 182 (5.6) | 7591 (6.0) | 126 346 (5.4) | 7228 (6.0) | 7228 (6.0) | ||||
| Qatari | 36 177 (12.0) | 235 972 (10.1) | 36 091 (12.4) | 36 091 (12.4) | 18 940 (14.9) | 235 972 (10.1) | 18 813 (15.6) | 18 813 (15.6) | ||||
| Sri Lankan | 9598 (3.2) | 59 805 (2.6) | 9249 (3.2) | 9249 (3.2) | 3190 (2.5) | 59 805 (2.6) | 2950 (2.5) | 2950 (2.5) | ||||
| Sudanese | 8231 (2.7) | 55 207 (2.4) | 8017 (2.8) | 8017 (2.8) | 3638 (2.9) | 55 207 (2.4) | 3430 (2.9) | 3430 (2.9) | ||||
| Other nationalitiese | 48 201 (16.0) | 565 244 (24.3) | 43 703 (15.0) | 43 703 (15.0) | 25 719 (20.2) | 565 244 (24.3) | 22 692 (18.8) | 22 692 (18.8) | ||||
| Comorbidity count | ||||||||||||
| None | 241 571 (80.0) | 1 991 109 (85.5) | 0.15 | 235 153 (80.9) | 235 153 (80.9) | 0.00 | 104 077 (81.9) | 1 991 109 (85.5) | 0.15 | 100 533 (83.4) | 100 533 (83.4) | 0.00 |
| 1–2 | 48 776 (16.2) | 268 390 (11.5) | 45 342 (15.6) | 45 342 (15.6) | 20 547 (16.2) | 268 390 (11.5) | 18 271 (15.2) | 18 271 (15.2) | ||||
| 3+ | 11 596 (3.8) | 69 540 (3.0) | 10 143 (3.5) | 10 143 (3.5) | 2451 (1.9) | 69 540 (3.0) | 1679 (1.4) | 1679 (1.4) | ||||
IQR denotes interquartile range and SMD standardized mean difference.
Individuals with a documented primary SARS-CoV-2 infection were exact-matched in a 1:1 ratio by sex, 10-year age group, nationality, comorbidity count and calendar week of the SARS-CoV-2 test to the first eligible infection-naïve individual.
SMD is the difference in the mean of a covariate between groups divided by the pooled standard deviation. An SMD < 0.1 indicates adequate matching.
SMD is for the mean difference between groups divided by the pooled standard deviation.
Nationalities were chosen to represent the most populous groups in Qatar.
These comprise 150 other nationalities in the unmatched primary-infection cohort and 183 other nationalities in the unmatched infection-naïve cohort, and 133 other nationalities in the matched primary-infection cohort and 133 other nationalities in the matched infection-naïve cohort in the Pre-Omicron Reinfection Study. These also comprise 145 other nationalities in the unmatched primary-infection cohort and 183 other nationalities in the unmatched infection-naïve cohort, and 123 other nationalities in the matched primary-infection cohort and 123 other nationalities in the matched infection-naïve cohort in the Omicron Reinfection Study.