Table 2. Characteristics of Vaccinated and Unvaccinated Omicron Cases and SARS-CoV-2–Negative Controlsa.
| Characteristic | Unvaccinated (n = 5471)b | 2 Doses (n = 105 118)b | Standardized differencec,d | 3 Doses (n = 19 585)b | Standardized differencec,e |
|---|---|---|---|---|---|
| Age, mean (SD), y | 37.1 (15.1) | 39.5 (15.1) | 0.16 | 52.1 (18.8) | 0.88 |
| Age group, y | |||||
| 18-29 | 2085 (38.1) | 32 809 (31.2) | 0.15 | 2866 (14.6) | 0.55 |
| 30-39 | 1545 (28.2) | 27 034 (25.7) | 0.06 | 3275 (16.7) | 0.28 |
| 40-49 | 796 (14.5) | 18 474 (17.6) | 0.08 | 2558 (13.1) | 0.04 |
| 50-59 | 519 (9.5) | 14 515 (13.8) | 0.14 | 3583 (18.3) | 0.26 |
| 60-69 | 298 (5.4) | 8437 (8.0) | 0.10 | 3097 (15.8) | 0.34 |
| 70-79 | 137 (2.5) | 2698 (2.6) | 0 | 2784 (14.2) | 0.43 |
| ≥80 | 91 (1.7) | 1151 (1.1) | 0.05 | 1422 (7.3) | 0.27 |
| Sex | |||||
| Female | 2880 (52.6) | 60 666 (57.7) | 0.10 | 12 587 (64.3) | 0.24 |
| Male | 2591 (47.4) | 44 452 (42.3) | 0.10 | 6998 (35.7) | 0.24 |
| Any comorbidityf | 2088 (38.2) | 41 929 (39.9) | 0.04 | 11 028 (56.3) | 0.37 |
| SARS-CoV-2 tests within 3 mo before Dec 14, 2020, No. | |||||
| 0 | 4435 (81.1) | 78 274 (74.5) | 0.16 | 13 196 (67.4) | 0.32 |
| 1 | 780 (14.3) | 19 987 (19.0) | 0.13 | 3875 (19.8) | 0.15 |
| ≥2 | 256 (4.7) | 6857 (6.5) | 0.08 | 2514 (12.8) | 0.29 |
| Receipt of 2019-2020 and/or 2020-2021 influenza vaccination | 409 (7.5) | 33 148 (31.5) | 0.64 | 11 052 (56.4) | 1.23 |
| Public health unit regiong | |||||
| Central East | 531 (9.7) | 7971 (7.6) | 0.08 | 1468 (7.5) | 0.08 |
| Central West | 1032 (18.9) | 20 604 (19.6) | 0.02 | 3454 (17.6) | 0.03 |
| Durham | 309 (5.6) | 7351 (7.0) | 0.06 | 1080 (5.5) | 0.01 |
| Eastern | 293 (5.4) | 6268 (6.0) | 0.03 | 1314 (6.7) | 0.06 |
| North | 472 (8.6) | 5802 (5.5) | 0.12 | 1509 (7.7) | 0.03 |
| Ottawa | 165 (3.0) | 5398 (5.1) | 0.11 | 1132 (5.8) | 0.14 |
| Peel | 666 (12.2) | 12 730 (12.1) | 0 | 1743 (8.9) | 0.11 |
| Southwest | 790 (14.4) | 10 649 (10.1) | 0.13 | 2447 (12.5) | 0.06 |
| Toronto | 893 (16.3) | 19 896 (18.9) | 0.07 | 4045 (20.7) | 0.11 |
| York | 283 (5.2) | 8018 (7.6) | 0.10 | 1323 (6.8) | 0.07 |
| Household income quintileg,h | |||||
| 1 | 1253 (22.9) | 15 708 (14.9) | 0.20 | 2552 (13.0) | 0.26 |
| 2 | 1182 (21.6) | 18 931 (18.0) | 0.09 | 3202 (16.3) | 0.13 |
| 3 | 1100 (20.1) | 20 940 (19.9) | 0 | 3561 (18.2) | 0.05 |
| 4 | 969 (17.7) | 23 240 (22.1) | 0.11 | 4425 (22.6) | 0.12 |
| 5 | 923 (16.9) | 25 829 (24.6) | 0.19 | 5750 (29.4) | 0.30 |
| Essential workers quintileg,i | |||||
| 1 | 783 (14.3) | 24 992 (23.8) | 0.24 | 5660 (28.9) | 0.36 |
| 2 | 1042 (19.0) | 26 526 (25.2) | 0.15 | 4962 (25.3) | 0.15 |
| 3 | 1142 (20.9) | 20 899 (19.9) | 0.02 | 3753 (19.2) | 0.04 |
| 4 | 1205 (22.0) | 17 717 (16.9) | 0.13 | 2964 (15.1) | 0.18 |
| 5 | 1231 (22.5) | 14 333 (13.6) | 0.23 | 2091 (10.7) | 0.32 |
| Persons per dwelling quintileg,j | |||||
| 1 | 1011 (18.5) | 18 695 (17.8) | 0.02 | 4000 (20.4) | 0.05 |
| 2 | 1132 (20.7) | 16 613 (15.8) | 0.13 | 3357 (17.1) | 0.09 |
| 3 | 749 (13.7) | 13 690 (13.0) | 0.02 | 2677 (13.7) | 0 |
| 4 | 1302 (23.8) | 25 913 (24.7) | 0.02 | 4781 (24.4) | 0.01 |
| 5 | 1202 (22.0) | 29 507 (28.1) | 0.14 | 4613 (23.6) | 0.04 |
| Self-identified visible minority group quintileg,k,l | |||||
| 1 | 992 (18.1) | 14 273 (13.6) | 0.12 | 3104 (15.8) | 0.06 |
| 2 | 1014 (18.5) | 17 891 (17.0) | 0.04 | 3624 (18.5) | 0 |
| 3 | 988 (18.1) | 20 750 (19.7) | 0.04 | 4247 (21.7) | 0.09 |
| 4 | 1135 (20.7) | 24 669 (23.5) | 0.07 | 4509 (23.0) | 0.06 |
| 5 | 1274 (23.3) | 26 886 (25.6) | 0.05 | 3947 (20.2) | 0.08 |
| Week of test | |||||
| Dec 6 to Dec 12, 2021 | 1580 (28.9) | 27 714 (26.4) | 0.06 | 2538 (13.0) | 0.40 |
| Dec 13 to Dec 19, 2021 | 1841 (33.7) | 38 780 (36.9) | 0.07 | 5518 (28.2) | 0.12 |
| Dec 20 to Dec 26, 2021 | 2050 (37.5) | 38 624 (36.7) | 0.02 | 11 529 (58.9) | 0.44 |
| Prior positive SARS-CoV-2 test result | 261 (4.8) | 3658 (3.5) | 0.06 | 455 (2.3) | 0.13 |
| Vaccination status | |||||
| Unvaccinated | 5471 (100) | NA | NA | NA | NA |
| Received 2-dose primary series only with ≥1 mRNA vaccine | NA | 105 118 (100) | NA | NA | NA |
| Received BNT162b2 for third dose | NA | NA | NA | 16 007 (81.7) | NA |
| Received mRNA-1273 for third dose | NA | NA | NA | 3578 (18.3) | NA |
| Time since second dose, d | |||||
| 7-59 | NA | 2485 (2.4) | NA | NA | NA |
| 60-119 | NA | 7772 (7.4) | NA | NA | NA |
| 120-179 | NA | 69 265 (65.9) | NA | NA | NA |
| 180-239 | NA | 23 658 (22.5) | NA | NA | NA |
| ≥240 | NA | 1938 (1.8) | NA | NA | NA |
| Time since third dose, d | |||||
| 0-6 | NA | NA | NA | 6767 (34.6) | NA |
| 7-59 | NA | NA | NA | 11 921 (60.9) | NA |
| ≥60 | NA | NA | NA | 897 (4.6) | NA |
| Interval between first and second doses, d | |||||
| 15-34 | NA | 14 355 (13.7) | NA | 3392 (17.3) | NA |
| 35-55 | NA | 39 792 (37.9) | NA | 4334 (22.1) | NA |
| ≥56 | NA | 50 971 (48.5) | NA | 11 859 (60.6) | NA |
| Interval between second and third doses, d | |||||
| ≤111 | NA | NA | NA | 250 (1.3) | NA |
| 112-167 | NA | NA | NA | 1739 (8.9) | NA |
| ≥168 | NA | NA | NA | 17 596 (89.8) | NA |
Abbreviation: NA, not applicable.
Participants included adults with COVID-19–relevant symptoms who were tested for SARS-CoV-2 from December 6 to 26, 2021.
Data are presented as number (percentage) of participants unless otherwise indicated.
Standardized differences greater than 0.10 were considered clinically relevant.
Comparison of participants who had received 2 doses with unvaccinated participants.
Comparison of participants who had received 3 doses with unvaccinated participants.
Comorbidities included chronic respiratory diseases, chronic heart diseases, hypertension, diabetes, immunocompromising conditions owing to underlying diseases or therapy, autoimmune diseases, chronic kidney disease, advanced liver disease, dementia/frailty, and history of stroke or transient ischemic attack.
The sum of counts does not equal the column total because of individuals with missing information (<1.0%) for this characteristic.
Household income quintiles have variable cutoff values in each city or census area to account for cost of living. A dissemination area being in quintile 1 means it is among the lowest 20% of dissemination areas in its city by income.
Percentage of people in the area working in the following occupations: sales and service occupations; trades, transport and equipment operators, and related occupations; natural resources, agriculture, and related production occupations; and occupations in manufacturing and utilities. Census counts for people were randomly rounded up or down to the nearest number divisible by 5, which caused some minor imprecision. Quintile 1 was 0% to <32.5%; quintile 2, 32.5% to <42.3%; quintile 3, 42.3% to <50.0%; quintile 4, 50.0% to <57.5%; and quintile 5, 57.5% to 100%.
Quintile 1 was 0 to 2.1; quintile 2, 2.2 to 2.4; quintile 3, 2.5 to 2.6; quintile 4, 2.7 to 3.0; and quintile 5, 3.1 to 5.7.
Census counts were randomly rounded up or down to the nearest number divisible by 5, which caused some minor imprecision. Quintile 1 was 0.0% to 2.23%; quintile 2, 2.24% to 7.53%; quintile 3, 7.54% to 18.68%; quintile 4, 18.69% to 43.52%; and quintile 5, 43.53% to 100%.
Non-Aboriginal peoples who are not White, consisting mainly of Arab, Black, Chinese, Filipino, Korean, Japanese, Latin American, South Asian, Southeast Asian, and West Asian groups.28