Demographic characteristics, clinical characteristics and clinical outcomes among 195 adults admitted to intensive care units (ICU) with SARS-CoV-2 infection by vaccination status and period of variant predominance—one hospital, California, 15 July 2021–23 September 2021 (Delta period) and 21 December 2021–27 January 2022 (Omicron period)
| Characteristic | No (%) | ||||||||
| Total ICU admissions (n=195) | Unvaccinated (n=129) | Fully vaccinated (n=59) | |||||||
| Delta period | Omicron period | P value | Delta period | Omicron period | P value | Delta period | Omicron period | P value | |
| Total | 79 | 116 | - | 55 | 74 | - | 20 | 39 | - |
| Vaccination status*† | |||||||||
| Unvaccinated | 55 (69.6) | 74 (63.8) | 0.443 | 55 (100) | 74 (100) | - | - | - | - |
| At least one dose | 24 (30.4) | 42 (36.2) | 0.443 | - | - | - | 20 (100) | 39 (100) | - |
| Fully vaccinated | 20 (25.3) | 39 (33.6) | 0.267 | - | - | - | 20 (100) | 39 (100) | - |
| Fully vaccinated and booster dose‡ | - | 5 (4.3) | - | - | - | - | - | 5 (12.8) | - |
| Age, years, median (IQR) | 62 (36) | 65 (26) | 0.116 | 45 (32) | 63 (26) | 0.002 | 75 (15) | 68 (18) | 0.037 |
| Women | 26 (32.9) | 42 (36.2) | 0.650 | 20 (36.4) | 31 (41.9) | 0.587 | 5 (25.0) | 11 (28.2) | 1.000 |
| Race and ethnicity | |||||||||
| White, non-Hispanic | 27 (34.2) | 46 (39.7) | 0.455 | 13 (23.6) | 27 (36.5) | 0.129 | 13 (65.0) | 16 (41.0) | 0.103 |
| Black, non-Hispanic | 19 (24.1) | 18 (15.5) | 0.142 | 14 (25.5) | 11 (14.9) | 0.177 | 3 (15.0) | 7 (18.0) | 1.000 |
| Hispanic | 17 (21.5) | 30 (25.9) | 0.609 | 15 (27.3) | 21 (28.4) | 1.000 | 2 (10.0) | 9 (23.1) | 0.302 |
| Asian, non-Hispanic | 1 (1.3) | 5 (4.3) | 0.404 | 1 (1.8) | 3 (4.1) | 0.636 | 0 (0.0) | 2 (5.1) | 0.544 |
| Other, non-Hispanic§ | 15 (19.0) | 17 (14.7) | 0.437 | 12 (21.8) | 12 (16.2) | 0.495 | 2 (10.0) | 5 (12.8) | 1.000 |
| Comorbidities | |||||||||
| Any | 46 (58.2) | 56 (48.3) | 0.191 | 34 (61.8) | 34 (46.0) | 0.079 | 11 (55.0) | 20 (51.3) | 1.000 |
| Obesity (BMI >30 kg/m2) | 29 (36.7) | 41 (35.3) | 0.880 | 18 (32.7) | 30 (40.5) | 0.462 | 10 (50.0) | 11 (28.2) | 0.151 |
| Chronic pulmonary disease¶ | 6 (7.6) | 1 (0.9) | 0.018 | 6 (10.9) | 0 (0.0) | 0.005 | 0 (0.0) | 1 (2.6) | 1.000 |
| Cardiovascular disease** | 8 (10.1) | 12 (10.3) | 1.000 | 7 (12.7) | 4 (5.4) | 0.203 | 1 (5.0) | 6 (15.4) | 0.404 |
| Hypertension | 19 (24.1) | 17 (14.7) | 0.132 | 19 (34.6) | 7 (9.5) | 0.001 | 0 (0.0) | 8 (20.5) | 0.042 |
| Diabetes Mellitus | 9 (11.4) | 13 (11.2) | 1.000 | 9 (16.4) | 6 (8.1) | 0.172 | 0 (0.0) | 7 (18.0) | 0.083 |
| Renal | 6 (7.6) | 11 (9.5) | 0.798 | 6 (10.9) | 3 (4.1) | 0.169 | 0 (0.0) | 7 (18.0) | 0.083 |
| ICU admission not likely due to COVID-19 | 7 (8.9) | 20 (17.2) | 0.138 | 4 (7.3) | 10 (13.5) | 0.392 | 2 (10.0) | 10 (25.6) | 0.192 |
| COVID-19 therapies received | |||||||||
| Any | 69 (87.3) | 86 (74.1) | 0.030 | 49 (89.1) | 57 (77.0) | 0.104 | 16 (80.0) | 26 (66.7) | 0.370 |
| Dexamethasone | 64 (81.0) | 82 (70.7) | 0.130 | 45 (81.8) | 55 (74.3) | 0.395 | 16 (80.0) | 24 (61.5) | 0.239 |
| Remdesivir | 58 (73.4) | 57 (49.1) | 0.001 | 41 (74.6) | 37 (50.0) | 0.006 | 14 (70.0) | 18 (46.2) | 0.103 |
| Tocilizumab | 38 (48.1) | 9 (7.8) | <0.001 | 27 (49.1) | 5 (6.8) | <0.001 | 9 (45.0) | 4 (10.3) | 0.006 |
| Baricitinib | 1 (1.3) | 26 (22.4) | <0.001 | 0 (0.0) | 20 (27.0) | <0.001 | 1 (5.0) | 5 (12.8) | 0.653 |
| Casirivimab | 2 (2.5) | 1 (0.9) | 0.567 | 0 (0.) | 1 (1.4) | 1.000 | 1 (5.0) | 0 (0.0) | 0.339 |
| Convalescent plasma | 2 (2.5) | 1 (0.9) | 0.567 | 1 (1.8) | 1 (1.4) | 1.000 | 1 (5.0) | 0 (0.0) | 0.339 |
| Sequential Organ Failure Assessment (SOFA) score, median (IQR)†† | 9 (7) | 8 (7) | 0.091 | 9 (6) | 8 (8) | 0.105 | 8 (6.5) | 8 (5) | 0.506 |
| Invasive mechanical ventilation (IMV) | 46 (58.2) | 61 (52.6) | 0.466 | 37 (67.3) | 42 (56.8) | 0.274 | 8 (40.0) | 15 (44.1) | 1.000 |
| IMV duration among those receiving IMV, days, median (IQR) | 18 (19) | 8 (21) | 0.006 | 19 (22) | 8.5 (21) | 0.018 | 12 (7) | 7 (20) | 0.077 |
| Rescue therapies received among those receiving IMV | |||||||||
| Any | 37 (80.4) | 30 (49.2) | 0.001 | 32 (86.5) | 21 (50.0) | 0.001 | 5 (62.5) | 8 (53.3) | 1.000 |
| Prone | 25 (54.4) | 27 (44.3) | 0.333 | 22 (59.5) | 19 (45.2) | 0.261 | 3 (37.5) | 7 (46.7) | 1.000 |
| Neuromuscular blockade | 26 (56.5) | 22 (36.1) | 0.049 | 24 (64.9) | 17 (40.5) | 0.042 | 2 (25.0) | 5 (33.3) | 1.000 |
| Inhale nitric oxide | 21 (45.7) | 20 (32.8) | 0.229 | 18 (48.6) | 16 (38.1) | 0.371 | 3 (37.5) | 4 (26.7) | 0.657 |
| Extracorporeal membrane oxygenation | 13 (28.3) | 5 (8.2) | 0.009 | 12 (32.4) | 5 (11.9) | 0.032 | 1 (12.5) | 0 (0.0) | 0.348 |
| Tracheostomy, among those receiving IMV | 15 (32.6) | 12 (19.7) | 0.177 | 15 (40.5) | 8 (19.1) | 0.048 | 0 (0.0) | 4 (26.7) | 0.257 |
| Length of stay, days, median (IQR) | 20 (17) | 13 (25.5) | 0.036 | 21 (30) | 14.5 (26) | 0.033 | 17 (15) | 13.5 (31) | 0.940 |
| Length of stay in acute care, days, median (IQR)‡‡ | 9 (13) | 7 (11) | 0.538 | 9 (13) | 6 (12) | 0.535 | 8 (10.5) | 9 (10) | 0.752 |
| Length of stay in intensive care, days, median (IQR) | 9 (19) | 5 (12) | 0.100 | 12 (23) | 5 (15) | 0.037 | 3.5 (10.5) | 5 (9) | 0.678 |
| Died in hospital | 27 (34.2) | 39 (33.6) | 1.000 | 17 (30.9) | 27 (36.5) | 0.575 | 10 (50.0) | 10 (29.4) | 0.154 |
P-values <0.05 are bolded.
*Vaccination status was ascertained from the California Immunisation Registry. Booster status was unavailable for hospitalisations before 1 December 2021. Fully vaccinated persons hospitalised during Delta period were assumed not to have received a booster dose because booster doses were not recommended during the period of Delta predominance.
†Partially vaccinated adults were not included in the analyses stratified by vaccination status because of small sample size. However, they were included in overall proportions and comparisons not stratified by vaccination status; thus, the total number of patients exceeds the sum of fully vaccinated and unvaccinated patients.
‡Omicron-period patients who received a booster dose were excluded from comparisons of illness severity indicators (SOFA, IMV, rescue therapies, tracheostomy, length of stay and death while hospitalised) among fully vaccinated persons.
§Includes Native Hawaiian, other Pacific Islander, American Indian, and Alaska Native persons, and persons of unknown race or ethnicity.
¶Includes chronic obstructive pulmonary disease, pulmonary fibrosis and asthma.
**Includes coronary artery disease, congestive heart failure, arrythmias, valvular heart disease, stroke and peripheral vascular disease.
††Highest SOFA score during hospital admission is reported.
‡‡Acute care refers to hospitalisation in a lower level of care than intensive care.
BMI, body mass index.