Table 1 Clinical characteristics of all patients included in the study

Sex, (female), n(%)

666

328 (49.2%)

Age (IQR)

666

67 (53–77)

Smoking, n(%)

666

198 (29.7%)

COPD*, n(%)

666

160 (24%)

Pregnancy, n(%)

666

5 (0.8%)

Obesity, n(%)

666

93 (14%)

Cardiac disease, n(%)

666

221 (33.2%)

Chronic kidney disease, n(%)

666

84 (12.6%)

Diabetes, n(%)

666

192 (28%)

Immunosuppression, n(%)

666

 HIV**, n(%)

45 (6.8%)

 Malignancy, n(%)

42 (6.3%)

 Corticotherapy, n(%)

18 (2.7%)

 Others, n(%)

31 (4.7%)

Vaccinated, n(%)

666

258 (38.7%)

Subtype, n(%)

666

H1N1

242 (36.3%)

H3N2

241 (36.2%)

Influenza A no subtype

33 (5%)

Influenza B

150 (22.5%)

Cough, n(%)

573 (86%)

Fever, n(%)

476 (71.5%)

Myalgia, n(%)

166 (24.9%)

Dyspnea, n(%)

666

446 (67%)

State of confusion, n(%)

666

64 (9.6%)

Heart rate, median (IQR), n total

650

96 (82–109)

Systolic blood pressure [mmHg], median (IQR), n total

655

131 (113–147)

Respiratory frequency, median (IQR), n

176

26 (20–32)

Oxygen saturation [%], median (IQR), n

655

93 (90–96)

Oxygen saturation < 93%, n(%)

655

262 (40%)

Horowitz Index (PaO₂/FiO₂⁾, median (IQR), n

527

276 (242–309)

Alveolar-arterial gradient, median (IQR), n

544

46 (38–55)

Alveolar-arterial gradient adjusted for age, median (IQR), n

595

17.4 (14.3–19.7)

Lymphocyte [x10⁹/L] median (IQR), n

666

8155 (6000–11,400)

Haematocrit [%], median (IQR), n

664

39.1 (34.7–42.7)

Platelet [x109/L], median (IQR)

666

201,500 (151,000–258,000)

Creatinine [mg/dl], median (IQR), n

665

0.9 (0.7–1.1)

Urea [mg/d], median (IQR), n

659

36 (28–53)

Albumin [mg/dl], median (IQR), n

474

34.6 (31-37.3)

C-reactive protein [mg/dl], median (IQR), n

510

5.1 (2-11.9)

Pneumonia, n(%)

666

185 (27.8%)

Pleural effusion, n (%)

666

28 (4.2%)

Septic shock, n(%)

666

50 (7.5%)

Mechanical ventilation, n(%)

666

67 (10.1%)

ARDS***, n (%)

666

11 (1.7%)

Intensive care unit admission, n(%)

666

73 (11%)

Death, n(%)

666

39 (5.9%)

ICU admission and death

666

93 (14%)