Table 1.
Characteristics of patients admitted to hospital without covid-19 (controls) and with covid-19 (cases) during periods of dominant SARS-CoV-2 variant: alpha (11 March to 3 July 2021), delta (4 July to 25 December 2021), and omicron (26 December 2021 to 14 January 2022). Values are numbers (percentages) unless stated otherwise
| Characteristics | Controls (n=5962) | Cases by variant period | ||
|---|---|---|---|---|
| Alpha (n=1072) | Delta (n=3951) | Omicron (n=559) | ||
| Median (IQR) age (years) | 63 (50-72) | 56 (43-65.5) | 57 (43-69) | 62 (49-73) |
| Women | 2975 (49.9) | 519 (48.4) | 1803 (45.6) | 264 (47.2) |
| Race and ethnicity: | ||||
| Non-Hispanic white | 3611 (60.6) | 484 (45.1) | 2183 (55.3) | 279 (49.9) |
| Non-Hispanic black | 1240 (20.8) | 285 (26.6) | 820 (20.8) | 127 (22.7) |
| Hispanic, any race | 772 (12.9) | 220 (20.5) | 695 (17.6) | 111 (19.9) |
| Non-Hispanic, other | 253 (4.2) | 63 (5.9) | 179 (4.5) | 33 (5.9) |
| Unknown | 86 (1.4) | 20 (1.9) | 74 (1.9) | 9 (1.6) |
| US Census region: | ||||
| North east | 885 (14.8) | 158 (14.7) | 686 (17.4) | 159 (28.4) |
| South | 2371 (39.8) | 395 (36.8) | 1544 (39.1) | 196 (35.1) |
| Midwest | 1374 (23.0) | 248 (23.1) | 978 (24.8) | 104 (18.6) |
| West | 1332 (22.3) | 271 (25.3) | 743 (18.8) | 100 (17.9) |
| Resident of long term care facility | 321/5778 (5.6) | 25/1039 (2.4) | 120/3795 (3.2) | 30/534 (5.6) |
| ≥1 hospital admission in past year | 3031/5537 (54.7) | 282/956 (29.5) | 1015/3682 (27.6) | 226/535 (42.2) |
| Current tobacco use | 1016/5302 (19.2) | 103/887 (11.6) | 366/3451 (10.6) | 59/470 (12.6) |
| Median (IQR) No of chronic conditions* | 2 (1-3) | 1 (1-3) | 1 (0-3) | 2 (1-3) |
| Categories of medical conditions*: | ||||
| Chronic cardiovascular disease | 4158 (69.7) | 589 (54.9) | 2141 (54.2) | 359 (64.2) |
| Chronic pulmonary disease | 1973 (33.1) | 231 (21.5) | 827 (20.9) | 151 (27.0) |
| Diabetes mellitus | 1962 (32.9) | 316 (29.5) | 1135 (28.7) | 164 (29.3) |
| Immunocompromising condition* | 1458 (24.5) | 172 (16.0) | 659 (16.7) | 138 (24.7) |
| Obesity | 2391/5900 (40.5) | 616/1056 (58.3) | 2099/3909 (53.7) | 260/556 (46.8) |
| Vaccination status: | ||||
| Unvaccinated | 2054 (34.5) | 953 (88.9) | 2871 (72.7) | 268 (47.9) |
| 2 doses (<150 days) | 2029 (34.0) | 119 (11.1) | 352 (8.9) | 34 (6.1) |
| 2 doses (≥150 days) | 1411 (23.7) | 0 (0) | 667 (16.9) | 177 (31.7) |
| 3 doses | 468 (7.8) | 0 (0) | 61 (1.5) | 80 (14.3) |
| Vaccine product received: | n=3908 | n=119 | n=1080 | n=291 |
| BNT162b2 (Pfizer-BioNTech) | 2269 (58.1) | 81 (68.1) | 708 (65.6) | 203 (69.8) |
| mRNA-1273 (Moderna) | 1615 (41.3) | 37 (31.1) | 368 (34.1) | 84 (28.9) |
| Mixed | 24 (0.6) | 1 (0.8) | 4 (0.4) | 4 (1.4) |
| Median (IQR) days since dose 3 | 41 (23-64) | — | 38 (23-65) | 69.5 (41.5-97) |
IQR=interquartile range.
See supplementary table S5 for baseline characteristics of cases limited to those with a sequencing confirmed variant.
Obtained using structured medical chart review and defined as one or more of the following: active solid organ cancer (active cancer defined as treatment for the cancer or newly diagnosed cancer in past six months), active hematologic cancer, HIV infection without AIDS, AIDS, congenital immunodeficiency syndrome, previous splenectomy, previous solid organ transplant, immunosuppressive drugs, systemic lupus erythematosus, rheumatoid arthritis, psoriasis, scleroderma, or inflammatory bowel disease, including Crohn’s disease and ulcerative colitis.