Table 1.
Characteristics of persons with SARS-CoV-2 infection in Northern California stratified by time periods of predominant Omicron SARS-CoV-2 variant (December 18, 2021-January 7, 2022) and Delta SARS-CoV-2 variant (July 5, 2021-November 30, 2021) transmission.
| Characteristic | All, N = 118,078 n (%) |
Omicron period, N = 48,101 n (%) |
Delta period, N = 69,977 n (%) |
p-value2 |
|---|---|---|---|---|
| Age, years1 | 37 (23, 52) | 37 (24, 51) | 37 (22, 53) | 0.002 |
| Age, years | <0.001 | |||
| 0-17 | 21,208 (18%) | 7,339 (15%) | 13,869 (20%) | |
| 18-39 | 43,310 (37%) | 19,285 (40%) | 24,025 (34%) | |
| 40-49 | 19,588 (17%) | 8,352 (17%) | 11,236 (16%) | |
| 50-59 | 15,907 (13%) | 6,694 (14%) | 9,213 (13%) | |
| 60-69 | 10,662 (9.0%) | 3,946 (8.2%) | 6,716 (9.6%) | |
| 70-79 | 4,967 (4.2%) | 1,681 (3.5%) | 3,286 (4.7%) | |
| 80+ | 2,331 (2.0%) | 699 (1.5%) | 1,632 (2.3%) | |
| Sex | <0.001 | |||
| Female | 64,416 (55%) | 27,280 (57%) | 37,136 (53%) | |
| Male | 53,662 (45%) | 20,821 (43%) | 32,841 (47%) | |
| Race/Ethnicity | <0.001 | |||
| LatinX/Hispanic Ethnicity | 33,047 (28%) | 13,428 (28%) | 19,619 (28%) | |
| Black/African Descent | 12,564 (11%) | 5,321 (11%) | 7,243 (10%) | |
| Asian Descent | 17,221 (15%) | 9,564 (20%) | 7,657 (11%) | |
| White/European or Middle Eastern Descent | 46,118 (39%) | 15,876 (33%) | 30,242 (43%) | |
| Other/Unknown | 9,128 (7.7%) | 3,912 (8.1%) | 5,216 (7.5%) | |
| Charlson co-morbidity index scores | <0.001 | |||
| Missing (no visits in prior year) | 10,836 (9.2%) | 3,769 (7.8%) | 7,067 (10%) | |
| Score 0 | 80,886 (69%) | 33,837 (70%) | 47,049 (67%) | |
| Score 1 | 15,119 (13%) | 6,285 (13%) | 8,834 (13%) | |
| Score 2 | 4,760 (4.0%) | 1,857 (3.9%) | 2,903 (4.1%) | |
| Score 3+ | 6,477 (5.5%) | 2,353 (4.9%) | 4,124 (5.9%) | |
| Chronic obstructive pulmonary disease | 12,718 (11%) | 5,218 (11%) | 7,500 (11%) | 0.5 |
| Diabetes | 10,334 (8.8%) | 4,031 (8.4%) | 6,303 (9.0%) | <0.001 |
| Atherosclerotic cardiovascular disease | 8,141 (6.9%) | 2,832 (5.9%) | 5,309 (7.6%) | <0.001 |
| Renal disease | 3,820 (3.2%) | 1,389 (2.9%) | 2,431 (3.5%) | <0.001 |
| Cancer | 1,938 (1.6%) | 739 (1.5%) | 1,199 (1.7%) | 0.019 |
| Rheumatologic disease | 972 (0.8%) | 364 (0.8%) | 608 (0.9%) | 0.036 |
| Dementia | 599 (0.5%) | 196 (0.4%) | 403 (0.6%) | <0.001 |
| Body mass index, kg/m2 | <0.001 | |||
| <25 | 35,300 (33%) | 14,849 (34%) | 20,451 (32%) | |
| 25-29.9 | 31,284 (29%) | 13,122 (30%) | 18,162 (29%) | |
| 30-34.9 | 21,781 (20%) | 8,696 (20%) | 13,085 (21%) | |
| 35-39.9 | 10,328 (9.6%) | 4,050 (9.2%) | 6,278 (10.0%) | |
| ≥40 | 8,370 (7.8%) | 3,304 (7.5%) | 5,066 (8.0%) | |
| COVID-19 vaccination | <0.001 | |||
| None | 49,690 (42%) | 10,635 (22%) | 39,055 (56%) | |
| Complete primary series | 52,310 (44%) | 24,608 (51%) | 27,702 (40%) | |
| Completed primary series + additional dose | 11,983 (10%) | 11,347 (24%) | 636 (0.9%) | |
| Other (partial/mixed/other) | 4,095 (3.5%) | 1,511 (3.1%) | 2,584 (3.7%) | |
| Prior SARS-CoV-2 infection | 3,499 (3.0%) | 2,786 (5.8%) | 713 (1.0%) | <0.001 |
| Anti-SARS-CoV-2 antibody outpatient treatment5 | 1,130 (1.0%) | 222 (0.5%) | 908 (1.3%) | <0.001 |
| Severe clinical outcomes | ||||
| Any hospitalization | 6,624 (5.6%) | 1,169 (2.4%) | 5,455 (7.8%) | <0.001 |
| Hospitalized with low flow oxygen support | 5,256 (4.5%) | 773 (1.6%) | 4,483 (6.4%) | <0.001 |
| Hospitalized with high flow oxygen support or non-invasive mechanical ventilation | 2,282 (1.9%) | 302 (0.6%) | 1,980 (2.8%) | <0.001 |
| Hospitalized with invasive mechanical ventilation | 591 (0.5%) | 70 (0.1%) | 521 (0.7%) | <0.001 |
| Died | 561 (0.5%) | 83 (0.2%) | 478 (0.7%) | <0.001 |
| Testing for SARS-CoV-2 variant | ||||
| Whole genome sequencing confirmed Delta variant, n/N (%) | 12,990/13,470 (96.4%) | 03 | 12,990/13,470 (96.4%) |
|
| Whole genome sequencing confirmed Omicron variant, n/N (%) | 6/13,470 (0.04%) | 03 | 6/13,470 (0.04%) | |
| Spike gene target failure confirmed probable Omicron infection, n/N (%) | 12,476/13,344 (93.5%) | 12,476/13,344 (93.5%) | 04 |
1
Median (IQR); n (%).
2
Wilcoxon rank sum test; Pearson's Chi-squared test.
3
No valid lineage results available for Omicron time period.
4
Spike gene target failure not tested prior to Omicron time period.
5
Treatment with bamlanivimab plus etesevimab, casirivimab plus imdevimab, or sotrovimab.