Table 1.
Patient characteristics.
| Variables | Number of cases | Subcategory | Total | Delta variant predominant period | Omicron variant predominant period | P value |
|---|---|---|---|---|---|---|
| Case number | 847 | 847 | 458 | 389 | ||
| Age (years), median (IQR) | 847 | 7.0 (2.0–13.0) | 8.0 (2.0–13.0) | 6.0 (1.0–12.0) | 0.004 | |
| Male sex, number (%) | 847 | 456 (53.8) | 245 (53.5) | 211 (54.2) | 0.836 | |
| Body weight, median (IQR) | 815 | 23.0 (11.8–45.1) | 25.9 (13.0–48.0) | 20.2 (10.1–40.0) | <0.001 | |
| Underlying disease, number (%) | 847 | Any underlying disease | 118 (13.9) | 53 (11.6) | 65 (16.7) | 0.036 |
| Bronchial asthma | 52 (6.1) | 24 (5.2) | 28 (7.2) | 0.253 | ||
| Congenital heart anomaly | 13 (1.5) | 5 (1.1) | 8 (2.1) | 0.276 | ||
| Obesity | 12 (1.4) | 10 (2.2) | 2 (0.5) | 0.045 | ||
| Congenital anomaly or chromosomal abnormality | 12 (1.4) | 4 (0.9) | 8 (2.1) | 0.159 | ||
| Diabetes without complications | 6 (0.7) | 4 (0.9) | 2 (0.5) | 0.693 | ||
| Hypertension | 2 (0.2) | 1 (0.2) | 1 (0.3) | 1 | ||
| Others | 33 (3.9) | 7 (1.5) | 26 (6.7) | <0.001 | ||
| Immunosuppressive condition, number (%) | 847 | 23 (2.7) | 3 (0.7) | 20 (5.1) | <0.001 | |
| Exposure within 14 days prior to admission | 844 | Travel abroad | 26 (3.1) | 17 (3.7) | 9 (2.3) | 0.336 |
| 842 | Close contact with COVID-19 cases | 633 (75.2) | 367 (80.5) | 266 (68.9) | <0.001 | |
| 847 | Family | 481 (56.8) | 300 (65.5) | 181 (46.5) | <0.001 | |
| 847 | Educational facility | 113 (13.3) | 46 (10.0) | 67 (17.2) | 0.002 | |
| 847 | Nonfamily roommates | 7 (0.8) | 2 (0.4) | 5 (1.3) | 0.257 | |
| 847 | Workplace | 1 (0.1) | 1 (0.2) | 0 (0.0) | 1.0 | |
| 847 | Healthcare facility | 6 (0.7) | 3 (0.7) | 3 (0.8) | 1.0 | |
| 847 | Others | 36 (4.3) | 18 (3.9) | 18 (4.6) | 0.614 | |
| Onset to hospitalization (days) | 763 | 2.0 (1.0–4.0) | 3.0 (1.0–4.0) | 1.0 (1.0–3.0) | <0.001 | |
| Past history of COVID-19 | 845 | 8 (0.9) | 8 (1.8)a | 0 (0.0) | 0.009 | |
| Number of patients with two doses of SARS-CoV-2vaccine | 847 | 50 (5.9) | 1 (0.2) | 49 (12.6) | <0.001 |
SARS-CoV-2, severe acute respiratory coronavirus type 2; VOC, variant of concern; IQR, interquartile range; NA, not applicable.
a
Among eight patients with a known history of COVID-19, five patients were diagnosed within the same Delta variant predominant period.