Characteristics | Severe H1N1 subgroup (n = 93) | General H1N1 subgroup (n = 338) | P value |
---|---|---|---|
Age (y), median (IQR) | 4.0 (2.3, 5.9) | 5.5 (4.1, 6.6) | < 0.001 |
Male, n (%) | 66 (71.0) | 184 (54.4) | 0.004 |
BMI (kg/m2), median (IQR) | 19.4 (18.1, 21.1) | 17.5 (16.3, 19.1) | < 0.001 |
Vaccination status, n (%) | Â | Â | Â |
 H1N1 vaccination | 4 (4.3) | 12 (3.6) | 0.735 |
 COVID-19 vaccination | 85 (91.4) | 315 (93.2) | 0.552 |
  One-dose vaccination | 21 (22.6) | 68 (20.1) | 0.603 |
  Two-dose vaccination | 48 (51.6) | 153 (45.3) | 0.277 |
  Three-dose vaccination | 16 (17.2) | 94 (27.8) | 0.038 |
Symptoms, n (%) | Â | Â | Â |
 Fever | 93 (100.0) | 327 (96.7) | 0.078 |
  Duration of fever (d), median (IQR) | 6.0 (5.0, 8.0) | 4.0 (3.0, 5.0) | < 0.001 |
  Fever peak (°C), median (IQR) | 39.1 (38.8, 39.6) | 39.0 (38.7, 39.4) | 0.022 |
 Cough | 88 (94.6) | 307 (90.8) | 0.241 |
 Rhinorrhea | 36 (38.7) | 121 (35.8) | 0.605 |
 Wheezing | 52 (55.9) | 79 (23.4) | < 0.001 |
 Sore throat | 19 (20.4) | 64 (18.9) | 0.746 |
 Headache | 12 (12.9) | 37 (10.9) | 0.599 |
 Myalgia | 17 (18.3) | 88 (26.0) | 0.123 |
 Seizures | 41 (44.1) | 37 (10.9) | < 0.001 |
 Drowsiness | 65 (69.9) | 85 (25.1) | < 0.001 |
 Diarrhea | 15 (16.1) | 34 (10.1) | 0.102 |
 Vomiting | 18 (19.4) | 44 (13.0) | 0.123 |
 Abdominal pain | 10 (10.8) | 22 (6.5) | 0.167 |
Laboratory findings, median (IQR) | Â | Â | Â |
 Leukocyte count (×109/L) | 9.5 (6.9, 12.4) | 5.7 (4.1, 7.4) | < 0.001 |
 Neutrophil proportion (%) | 56.1 (45.9, 68.2) | 44.5 (29.3, 57.4) | < 0.001 |
 Lymphocyte proportion (%) | 28.8 (15.3, 42.2) | 44.0 (30.9, 59.7) | < 0.001 |
  Proportion of CD3+T cells (%) | 58.5 (47.4, 66.8) | 70.6 (67.4, 74.2) | < 0.001 |
  Proportion of CD3+8+T cells (%) | 22.3 (16.7, 26.6) | 26.9 (22.8, 32.1) | < 0.001 |
  Proportion of CD3+4+T cells (%) | 28.7 (23.3, 34.6) | 37.7 (31.6, 43.5) | < 0.001 |
  Proportion of NK cells (%) | 13.2 (9.3, 19.7) | 12.6 (9.1, 16.2) | 0.199 |
  Proportion of B cells (%) | 19.3 (14.0, 29.5) | 18.8 (15.8, 21.6) | 0.086 |
 CRP (mg/L) | 23.5 (23.1, 25.1) | 14.6 (10.1, 17.0) | < 0.001 |
 IL-6 (pg/mL) | 28.7 (19.5, 48.9) | 19.3 (16.6, 28.4) | < 0.001 |
 IL-10 (pg/mL) | 23.7 (17.6, 29.0) | 14.9 (12.0, 19.6) | < 0.001 |
 TNF-α (pg/mL) | 13.2 (9.5, 18.8) | 7.3 (4.5, 12.7) | < 0.001 |
 CK-MB (U/L) | 53.2 (43.9, 74.4) | 43.9 (39.5, 50.0) | < 0.001 |
 hs-TnT (pg/mL) | 7.8 (4.2, 13.2) | 4.1 (2.6, 5.8) | < 0.001 |
 ALT (U/L) | 17.0 (13.0, 25.5) | 15.0 (12.0, 21.3) | 0.065 |
 AST (U/L) | 33.0 (26.0, 41.5) | 32.0 (23.0, 41.0) | 0.478 |
 Fibrinogen (g/L) | 4.1 (3.7, 4.9) | 3.8 (3.4, 4.6) | 0.002 |
Co-infection with SARS-CoV-2, n (%) | 18 (19.4) | 37 (10.9) | 0.031 |
Mechanical ventilation, n (%) | 20 (21.5) | 0 (0.0) | < 0.001 |
LOS (d), median (IQR) | 9.0 (8.0, 11.0) | 7.0 (6.0, 8.0) | < 0.001 |