Demographic and Clinical Characteristics
A total of 422 hospitalized patients with SARS-CoV-2 Omicron Variant BA.2 infection were included in the analysis. The features of the study population are shown in Table 1. In terms of age, the median age was 38 years (IQR, 14 to 58) for all the participants. The median age in asymptomatic and mild group were 39 years (IQR, 14 to 57) and 23.5 years (IQR, 14 to 54) respectively, and both of them were significantly younger than that in the moderate infection group (68 years, IQR, 51.8 to 70.5, P = 0.001). In terms of age group, for all the participants, 151 (35.8%) patients were aged 15–49 years; 132 (31.3%), 0–14 years; 73 (17.3%), 50–64 years; 66 (15.6%), ≥ 65 years; For mild group, 45 out of 102 patients (44.1%) were aged < 14 years, and the proportion was significantly higher than that in asymptomatic group patients (P < 0.01). For moderate group, 6 out of 9 patients (66.7%) were aged ≥ 65 years, and the proportion was significantly higher than that in asymptomatic group and mild pneumonia group (P < 0.001) (Table 1). Regarding sex, for all the participates, 215 out of 422 (50.9%) patients were female. For asymptomatic patients, 159 out of 311 (51.1%) patients were female. For symptomatic patients, 51 out of 102 (50.0%) and 5 out of 9 (55.6%) were female in mild and moderate, respectively.
Table 1
Baseline Characteristics of Patients Infected With the SARS-CoV-2 Omicron variant BA.2
| All patients N = 422 | Asymptomatic N = 311 | Mild N = 102 | Moderate N = 9 | P Value & |
Age (year), median (IQR) | 38.0 (14.0–58.0) | 39.0 (14.0–57.0) | 23.5 (14.0–54.0) | 68.0 (51.8–70.5)**## | 0.001 |
Range | | | | | |
0–14 | 132 (31.3) | 86 (27.7) | 45 (44.1)** | 1 (11.1) | 0.003 |
15–49 | 151 (35.8) | 120 (38.6) | 30 (29.4) | 1 (11.1) | 0.072 |
50–64 | 73 (17.3) | 60(19.3) | 12(11.8) | 1 (11.1) | 0.193 |
≥ 65 | 66 (15.6) | 45 (14.5) | 15 (14.7) | 6 (66.7)**## | < 0.001 |
Sex | | | | | |
Female | 215 (50.9) | 159 (51.1) | 51 (50.0) | 5 (55.6) | 0.943 |
Male | 207 (49.1) | 152 (48.9) | 51 (50.0) | 4 (44.4) | |
Comorbidities | 70 (16.6) | 46 (14.8) | 17 (16.7)## | 7 (77.8)** | < 0.001 |
Chronic respiratory diseases | 6 (1.4) | 4 (1.3) | 0 (0) | 2 (22.2)**## | < 0.001 |
Coronary heart disease | 12 (2.8) | 5 (1.6) | 4 (3.9) | 3 (33.3)**## | < 0.001 |
Hypertension | 49 (11.6) | 37 (11.9) | 9 (8.8) | 3 (33.3) | 0.085 |
Diabetes | 6 (1.4) | 6 (1.9) | 0 (0) | 0 (0) | 0.338 |
Cerebrovascular disease | 10 (2.4) | 7 (2.3) | 2 (2.0) | 1 (11.1) | 0.216 |
Epilepsy | 2 (0.5) | 1 (0.3) | 1 (1.0) | 0 (0) | 0.687 |
Encephalitis | 1 (0.2) | 0 (0) | 1 (1.0) | 0 (0) | 0.208 |
Gastritis | 4 (0.9) | 2 (0.6) | 1 (1.0) | 1 (11.1)**# | 0.006 |
Peptic ulcer | 1 (0.2) | 1 (0.3) | 0 (0) | 0 (0) | 0.836 |
Chronic kidney disease | 1 (0.2) | 0 (0) | 1 (1.0) | 0 (0) | 0.208 |
Malignancy | 11 (2.6) | 5 (1.6) | 3 (2.9) | 3 (33.3)**## | < 0.001 |
| | | | | (continued) |
Table 1. (continued) | | | | | |
| All patients N = 422 | Asymptomatic N = 311 | Mild N = 102 | Moderate N = 9 | P Value & |
Rheumatic disease | 2 (0.5) | 2 (0.6) | 0 (0) | 0 (0) | 0.699 |
Vaccination status prior to infection | | | | | |
Fully vaccinated | 252 (59.7) | 202 (65.0) | 47 (46.1)** | 2 (22.2)** | < 0.001 |
Partially vaccinated | 147 (34.8) | 95 (30.5) | 48 (47.1)** | 4 (44.4) | 0.008 |
Non-vaccinated | 23 (5.5) | 14 (4.5) | 7 (6.9) | 3 (33.3)**## | 0.001 |
Fever | | | | | |
Patients | 61 (14.5) | 0 (0) | 53 (52.0)** | 8 (88.9)**# | < 0.001 |
Temperature on admission (℃) | 36.6 (36.6–37.0) | 36.5 (36.5–36.7) | 37.5 (36.6–38.2)** | 38.6 (37.5–39)**# | < 0.001 |
Range | | | | | |
< 37.3℃ | 361 (85.5) | 311 (100) | 49 (52.9)** | 1 (22.2)** | < 0.001 |
37.3–38.0℃ | 31 (7.3) | 0 (0) | 29 (23.5)** | 2 (11.1)** | < 0.001 |
38.1–39.0℃ | 21 (5.0) | 0 (0) | 18 (17.6)** | 3 (33.3)** | < 0.001 |
> 39.0℃ | 9 (2.1) | 0 (0) | 6 (5.9)** | 3 (33.3)**## | < 0.001 |
Symptoms | | | | | |
Pharyngalgia | 19 (4.5) | 0 (0) | 18 (17.6)** | 1 (11.1)** | < 0.001 |
Dry throat | 29 (6.9) | 0 (0) | 25(24.5)** | 4 (44.4)** | < 0.001 |
Throat itching | 23 (5.5) | 0 (0) | 19 (18.6)** | 4 (44.4)** | < 0.001 |
Dry cough | 28 (6.6) | 0 (0) | 26 (25.5)** | 2 (22.2)** | < 0.001 |
Sputum production | 41 (9.7) | 0 (0) | 36 (35.3)** | 5 (55.6)** | < 0.001 |
Headache | 19 (4.5) | 0 (0) | 17(16.7)** | 2 (22.2)** | < 0.001 |
Palpitation | 4 (0.9) | 0 (0) | 2(2.0)* | 2 (22.2)**## | < 0.001 |
| | | | | (continued) |
Table 1. (continued) | | | | | |
| All patients N = 422 | Asymptomatic N = 311 | Mild N = 102 | Moderate N = 9 | P Value & |
Runny nose | 17 (4.0) | 0 (0) | 17 (16.7)** | 0 (0) | < 0.001 |
Blocked nose | 15 (3.6) | 0 (0) | 15 (14.7)** | 0 (0) | < 0.001 |
Fatigue | 46 (10.9) | 0 (0) | 40 (39.2)** | 6 (66.7)** | < 0.001 |
Shortness of breath | 5 (1.2) | 0 (0) | 1(1.0) | 4 (44.4)**## | < 0.001 |
Chest tightness | 9 (2.1) | 0 (0) | 4 (3.9)** | 5 (55.6)**## | < 0.001 |
Dizziness | 3 (0.7) | 0 (0) | 2 (2.0)* | 1 (11.1)** | < 0.001 |
Myalgia | 16 (3.8) | 0 (0) | 12 (11.8)** | 4 (44.4)**## | < 0.001 |
Abdominal pain | 2 (0.5) | 0 (0) | 2 (2.0)* | 0 (0) | 0.043 |
Diarrhea | 3 (0.7) | 0 (0) | 3 (2.9)** | 0 (0) | 0.009 |
Heart rate (bpm), median (IQR) | 80 (72–88) | 80 (72–88) | 80 (72–88) | 88(76–102) | 0.349 |
Respiratory rate (bpm), median (IQR) | 19 (18–20) | 19 (18–20) | 20 (18–20)** | 20 (18–22) | 0.008 |
Mean arterial pressure (mmHg), median (IQR) | 93 (88–100) | 94 (87–101) | 93 (87–98) | 101 (91–112) | 0.150 |
Treatment | | | | | |
Traditional Chinese medicine | 422 (100) | 311 (100) | 102 (100) | 9 (100) | - |
Intravenous antibiotics | 7 (1.7) | 5 (1.6) | 0 (0) | 2 (22.2)**## | < 0.001 |
Immunomodulatory drugs | 11 (2.6) | 7 (2.3) | 2 (2.0) | 2 (22.2)**## | 0.001 |
Anticoagulant | 9 (2.1) | 5 (1.6) | 2 (2.0) | 2 (22.2)**## | < 0.001 |
Oxygen therapy | | | | | |
Nonventilator | 416 (98.6) | 308 (99.0) | 102 (100) | 6 (66.7)**## | < 0.001 |
Nasal cannula | 2 (0.5) | 0 (0) | 0 (0) | 2 (22.2)**## | < 0.001 |
| | | | | (continued) |
Table 1. (continued) | | | | | |
| All patients N = 422 | Asymptomatic N = 311 | Mild N = 102 | Moderate N = 9 | P Value & |
Non-invasive | 1 (0.2) | 1 (0.3) | 0 (0) | 0 (0) | 0.836 |
Invasive | 3 (0.7) | 2 (0.6) | 0 (0) | 1 (11.1)**## | 0.001 |
Vasoconstrictive agents | 3 (0.7) | 2 (0.6) | 0 (0) | 1 (11.1)**## | 0.001 |
Admission to intensive care unit | 4 (0.9) | 2 (0.6) | 1 (1.0) | 1 (11.1)**# | 0.006 |
Hospital length of stay, days | 7.0 (5.0–20.0) | 8.0 (5.0–20.0) | 6.0 (5.0–11.0) | 24.0 (11.5–31.5)**## | 0.001 |
Duration of viral shedding after omicron variant onset, days | 16 (13–19) | 15 (12–19) | 16 (14–20)* | 19 (16.5–23)* | 0.008 |
Clinical outcomes | | | | | |
Discharged | 419 (99.3) | 309 (99.4) | 102 (100) | 8 (88.9)**## | 0.001 |
Died | 3 (0.7) | 2 (0.6) | 0 (0) | 1 (11.1)**## | 0.001 |
Data are expressed as median (IQR) or number (%). P values are from Kruskal-Wallis test or χ2 test. Bold values indicate that P value is less than 0.05; & Indicate results of comparison of asymptomatic infection versus mild versus moderate; ** Compared to asymptomatic group P < 0.01; * Compared to asymptomatic group P < 0.05; ## Compared to mild group P < 0.01; # Compared to mild group P < 0.05 |
Abbreviations: SARS-CoV-2, Severe acute respiratory syndrome Coronavirus-2 |
Of the 422 patients, 70 (16.6%) had 1 or more coexisting medical conditions. Hypertension [49 (11.6%)], coronary heart disease [12 (2.8%)], malignancy [11 (2.6%)], cerebrovascular disease [10 (2.4%)], Chronic respiratory diseases [6 (1.4%)], and diabetes [6 (1.4%)] were the most common coexisting conditions (Table 1). Compared with asymptomatic patients (n = 311), moderate patients (n = 9) were more likely to have underlying comorbidities, including malignancy [3 (33.3%) vs 5 (1.6%)], coronary heart disease [3 (33.3%) vs 5 (1.6%)], chronic respiratory diseases [2 (22.2%) vs 4 (1.3%)] (Table 1 and Fig. 1).
The most common symptoms at onset of illness were fever [61 (14.5%)], fatigue [46 (10.9%)], sputum production [41 (9.7%)], dry throat [29 (6.9%)], dry cough [28 (6.6%)], throat itching [23 (5.5%)], headache [19 (4.5%)], pharyngalgia [19 (4.5%)], Runny nose [17 (4%)], Myalgia [16 (3.8%)], and blockded nose [15 (3.6%)]. Less common symptoms were palpitation, shortness of breath, chest tightness, dizziness, abdominal pain, and diaeehea (Table 1).
Among the 422 patients hospitalized for omicron variant, 252 patients (59.7%) were fully vaccinated. 147 patients (34.8%) have received at least one dose of COVID-19 vaccine. Only 23 (5.5%) of 422 patients had never received any COVID-19 vaccine dose. Nonvaccination rate was significant difference between asymptomatic group and moderte group (4.5% vs 33.3%, p = 0.001), respectively. Among Omicron-period patients, vaccination was associated with lower likelihood of symptomatic COVID-19 versus unvaccinated patients (Table 1). Among inpatient during Omicron predominance, increasing vaccination was associated with lower likelihood of moderate infection (Table 1). Unvaccinated and older patients (> 65 years) are at increased risk of moderate infection (Fig. 2).
Heart rate, respiratory rate, and mean arterial pressure did not differ between asymptomatic group and moderte group (Table 1). These measures were recorded on day of hospital admission for all patients.
All of the patients received traditional Chinese medicine. 7 (1.7%) patients received intravenous antibiotics and 9 (2.1%) received anticoagulant. Intravenous antibiotics and anticoagulant use differed significantly between moderate group and asymptomatic group (Table 1). Immunomodulatory drugs were given to 11 patients (2.6%), with a higher percentage among those with moderate than asymptomatic (22.2% vs. 2.3%). oxygen therapy was administered in 1.4%. Of these 422 patients, 4 (0.9%) were admitted to the ICU, 3 (0.7%) underwent invasive ventilation, and 3 (0.7%) died. Vasoconstrictive agents were performed in 3 patients (0.7%) (Table 1).
For all patients, the median duration of viral shedding was 16.0 days (IQR, 13 to19) from illness onset, but the virus was continuously detectable until death. The median duration of viral shedding was 16.0 days (IQR, 14 to 20) in patients with mild group and 19.0 days (IQR, 16.5 to 23) in patients with moderate group, and both of them were longer than that in the asymptomatic infection group (15 days, IQR, 12 to 19, P < 0.05). The median duration of hospitalization in asymptomatic and mild group was 8.0 days (IQR, 5.0 to 20.0) and 6.0 days (IQR, 5.0 to 11.0) respectively, and both of them were significantly shorter than that in the moderate infection group (24 days, IQR, 11.5 to 31.5, P = 0.001).
Radiologic and Laboratory Findings
Table 2 shows the radiologic and laboratory findings on admission. Chest computed tomography scan revealed ground glass opacity [4 (0.9%)], patchy shadowing [5 (1.2%)], at presentation (Table 2). No radiographic or CT abnormality was found in 408 of 422 patients (96.7%) with asymptomatic group and mild group.
Table 2
Radiographic and Laboratory Findings of patients with the SARS-CoV-2 Omicron variant BA.2 on admission
| Reference values | All patients N = 422 | Asymptomatic N = 311 | Mild N = 102 | Moderate N = 9 | P Value & |
Abnormalities on chest CT | | | | | | |
Ground-glass opacity | | 4(1.0) | 0 (0) | 0 (0) | 4 (44.4)**## | < 0.001 |
Patchy shadowing | | 5 (1.2) | 0 (0) | 0 (0) | 5 (55.6)**## | < 0.001 |
Laboratory findings | | | | | | |
White blood cell count,×109/L | 4.0–10.0 | 5.36 (4.36–6.57) | 5.44 (4..48−6.56) | 5.11 (4.01–6.76) | 4.76 (3.37–7.07) | 0.725 |
Neutrophil count,×109/L | 2.0–7.0 | 3.09 (2.14–4.12) | 3.08 (2.12–3.92) | 3.15 (2.17–4.31) | 3.45 (1.58–4.25) | 0.596 |
Lymphocyte count,×109/L | 0.8−4.0 | 1.57 (1.21–2.19) | 1.71 (1.27–2.31) | 1.39 (1.13–2.03)* | 1.25 (0.59–1.65)* | 0.008 |
< 0.8 | | 28 (6.6) | 15 (4.8) | 9 (8.8) | 4(44.4)**## | < 0.001 |
Monocyte count,×109/L | 0.12–1.20 | 0.40 (0.33–0.53) | 0.40 (0.32–0.52) | 0.42 (0.34–0.61) | 0.42 (0.33–0.51) | 0.105 |
Haemoglobin, g/L | 110–150 | 140.0 (130.0−151.0) | 141.0(130.0−152.8) | 140.0 (131.3−147.8) | 118.0 (103.8–143.0) | 0.120 |
Anaemia | | 27 (6.4) | 19 (6.1) | 6 (5.9) | 2 (22.2) | 0.146 |
Platelet count,×109/L | 100–300 | 224.0 (181.0−275.0) | 230.0 (186.3−279.5) | 213.0 (171.0−260.5) | 240.0 (164.8–281.0) | 0.105 |
CRP, mg/L | 0–4 | 3.26 (0.84–8.26) | 2.63 (0.79–7.57) | 5.29 (1.51–11.31)** | 3.22 (2.73–51.12) | 0.010 |
≥ 4 | | 173 (41.0) | 114 (36.7) | 55 (53.9)** | 4 (44.4) | 0.009 |
PT, s | 10–14 | 12.2 (11.50–12.90) | 12.10 (11.50–12.70) | 12.55 (11.80–13.40)** | 11.65 (11.50−12.43) | 0.011 |
≥ 10 to ≤ 14 | | 393 (93.1) | 299 (96.1) | 86 (84.3)** | 8 (88.9) | < 0.001 |
> 14 | | 29 (6.9) | 12 (3.9) | 16 (15.7)** | 1 (11.1) | < 0.001 |
APTT, s | 22–38 | 29.20 (27.33–31.80) | 28.70 (27.00−31.58) | 30.45 (28.33−33.00)** | 29.65 (28.55–35.75) | 0.001 |
< 22 | | 1 (0.2) | 1 (0.3) | 0 (0) | 0/9 (0) | 0.836 |
≥ 22 to ≤ 38 | | 403 (95.5) | 300 (96.5) | 95 (93.1) | 8 (88.9) | 0.233 |
> 38 | | 18 (4.3) | 10 (3.2) | 7 (6.9) | 1 (11.1) | 0.169 |
| | | | | | (continued) |
Table 2. (continued) | | | | | | |
| Reference values | All patients N = 422 | Asymptomatic N = 311 | Mild N = 102 | Moderate N = 9 | P Value & |
Fibrinogen, g/L | 2–4 | 2.97 (2.62–3.36) | 2.97 (2.61–3.37) | 2.96 (2.62–3.19) | 3.24 (2.98–3.53) | 0.205 |
D-dimer, mg/L | 0–1 | 0.73 (0.63–0.89) | 0.71 (0.62–0.87) | 0.75 (0.63–0.92)* | 1.39 (0.82–3.80)**# | 0.001 |
> 1 | | 69 (16.4) | 41 (13.2) | 22 (21.6)* | 6 (66.7)**## | < 0.001 |
CKMB, U/L | 0−5.03 | 1.34 (0.94–2.09) | 1.42 (0.99–2.13) | 1.09 (0.80–1.73) | 1.37 (1.26–2.08) | 0.068 |
Myohemoglobin | 0–80.0 | 7.45 (5.16–12.26) | 7.86 (5.52–12.69) | 6.09 (4.41–8.79)** | 13.38 (5.97–18.73) | 0.01 |
> 80 | | 5 (1.2) | 5 (1.6) | 0 (0) | 0 (0) | 0.405 |
Hypersensitive troponin I >0.02, pg/mL | 0.02–0.06 | 1 (0.2) | 0 (0) | 0 (0) | 1 (11.1)**## | < 0.001 |
ALT, U/L | 0–41 | 15.91 (11.40−23.49) | 16.81 (12.63–24.04) | 13.16 (9.45–21.50)* | 15.38 (12.17–39.24) | 0.035 |
> 41 | | 24 (5.7) | 16 (5.1) | 6 (5.9) | 2 (22.2) | 0.092 |
AST, U/L | 0–37 | 19.46 (16.54–24.48) | 19.58 (17.01–24.32) | 18.40 (15.24–33.31) | 24.10 (18.39–45.61) | 0.32 |
Albumin, g/L | 40–55 | 44.01 (41.79–46.31) | 44.14 (41.98–46.48) | 43.76 (41.59–45.59) | 39.4 (34.40−45.91) | 0.094 |
Total Bilirubin, µmol/L | 5.1–23 | 8.15 (6.52–11.41) | 8.26 (6.52–11.63) | 8.03 (6.39–11.09) | 7.28 (6.15–10.13) | 0.624 |
BUN, mmol/L | 1.7–8.3 | 4.07 (3.36–4.80) | 4.09 (3.35–4.87) | 3.96 (3.33–4.64) | 4.21 (3.73–4.60) | 0.873 |
Creatinine, µmol/L | 70–115 | 55.54 (47.41–64.61) | 55.91 (47.43–65.45) | 54.31 (48.15–60.31) | 48.31 (41.48–57.02) | 0.338 |
Serum iron, µmol/L | 8.1–28.3 | 9.88 (5.91–15.19) | 10.73 (6.39–16.59) | 7.58 (5.25–12.68)** | 7.91 (4.38–10.54) | 0.004 |
< 8.1 | | 150 (35.5) | 94 (30.2) | 52 (51.0)** | 4 (80.0) | 0.001 |
Sodium, mmol/L | 136–145 | 140.19 (138.80−141.60) | 140.23 (138.89−141.62) | 140.17 (138.60−141.56) | 139.39 (137.33−141.04) | 0.386 |
Potassium, mmol/L | 3.5–5.3 | 4.48 (4.16–4.82) | 4.49 (4.21–4.84) | 4.38 (4.02–4.79) | 3.98 (3.63–4.36)**# | 0.007 |
< 3.5 | | 7 (1.7) | 4 (1.3) | 3 (2.9) | 0(0) | 0.486 |
≥ 3.5 to ≤ 5.3 | | 391 (92.7) | 287 (92.3) | 95 (93.1) | 9 (100) | 0.666 |
> 5.3 | | 24 (5.7) | 20 (6.4) | 4 (3.9) | 0 (0) | 0.483 |
Data are expressed as median (IQR) or number (%). P values are from Kruskal-Wallis test or χ2 test. Bold values indicate that P value is less than 0.05; & Indicate results of comparison of asymptomatic infection versus mild versus moderate; ** Compared to asymptomatic group P < 0.01; * Compared to asymptomatic group P < 0.05; ## Compared to mild group P < 0.01; # Compared to mild group P < 0.05 |
Abbreviations: SARS-CoV-2, Severe acute respiratory syndrome Coronavirus-2; CT, Computed tomography; CRP, C-reactive protein; PT, Prothrombin time; APTT, Activated partial thromboplastin time; CKMB, Creatine kinase-MB; ALT, Alanine aminotransferase; AST, Aspartate aminotransferase; BUN, Blood urea nitrogen; |
Regarding laboratory findings, lymphopenia (< 0.8×109/L) was observed in 28 (6.6%) upon admission, which were more common in moderate patients. 173 (41.0%) patients had elevated levels of CRP. Increased D-dimer (66.7% vs. 13.2%) was more common in moderate group than that in asymptomatic group (P < 0.001). We observed that markers for the tissue damage in kidney and liver including BUN, creatinine, AST, ALT, and total bilirubin were no significant difference between asymptomatic cases and moderate cases. In addition, decreased serum iron (51.0% vs. 30.2%, P < 0.01) were also more common in mild group than in asymptomatic group.