Abstract
Objective
The spread of the novel SARS-Cov-2 variant Omicron created a challenging public health situation in a number of countries. In March 2022, Omicron emerged in Changchun, China, and the number of patients infected rapidly increased. The prevalence of Omicron infection symptoms differs from that of Delta, with more upper airway clinical symptoms apparent. This study aimed to investigate the clinical and upper airway characteristics of the Omicron variant.
Materials and methods
In this retrospective study, we collected data from participants in Changchun who had tested positive for Omicron with quantitative polymerase chain reaction between 10 March and 30 May 2022 using telephone interviews. The questionnaire was designed by the research team based on the number of upper airway symptoms using the visual analogue scale. We also considered age, sex, vaccination status, general symptoms, and cure period.
Results
A total of 3715 patients (2056 males and 1659 females) with mild COVID-19 from the Omicron variant were included. The patients had a mean age of 38.63 ( ± 13.97) years (range 2–86 years). The vaccine uptake rate was 91.33 % (8.66 %, 4.58 %, 65.33 %, and 21.43 % had received zero, one, two, and three doses, respectively). The incidence of upper airway symptoms, including throat and nasal symptoms, was 54.21 %. Throat symptoms were the most common during Omicron infection (49.12 %). Nasal symptoms were also common (20.08 %). The incidence of lower airway symptoms was 25.60 %, and gastrointestinal symptoms was 10.87 %. The incidence of general symptoms was 55.26 %. The cure period ranged from three to 37 days, with a mean of 10.24 ± 4.69 days. We compared the upper airway symptom severity for Omicron among different vaccination statuses and found no differences.
Conclusions
The main clinical characteristics of the SARS-Cov-2 Omicron variant are upper airway symptoms and general symptoms. Fever remains the most common symptom, followed by mild dry cough. There was no association between Omicron infection and COVID-19 vaccines, and the vaccination status might have been ineffective against upper airway symptom severity by Omicron.
Keywords: Omicron, Upper airway symptom, Clinical characteristic
Introduction
The SARS-Cov-2 variant Omicron (B.1.1.529) was first reported to the World Health Organisation in November 2021. Omicron carries 34 more mutations than other variants [1], leading to an increased spread of COVID-19. The spread of this variant created a challenging and threatening public health situation in a number of countries and caused global panic. Therefore, it is vital to investigate the clinical characteristics of this new variant to control this disease.
Although Omicron appears to spread more easily, several studies have suggested that the variant is associated with decreased severity and mortality compared to the Delta variant [2], [3]. A study from the United Kingdom investigated the prevalence of symptoms of 4990 Omicron cases using an app, suggesting that a sore throat was more common during Omicron than Delta and that there was less involvement of the lower respiratory tract [4]. Therefore, it appears that Omicron causes less severe disease. However, no detailed published literature has investigated the characteristics of upper airway symptoms and their severity in people with different vaccination statuses.
This study aimed to determine the clinical characteristics, especially upper airway symptoms, the cure period, and the differences in upper airway symptoms in people with different vaccination statuses.
Methods
Study design and participants
This was a retrospective cohort study involving 3715 patients with mild COVID-19 from the Omicron variant in Fangcang Shelter Hospitals (Changchun, China) between 10 March and 30 May 2022. All patients with laboratory-confirmed Omicron were eligible for participation. The inclusion and exclusion criteria for the patients are presented in the Appendix (p1).
This study was approved by the Research Ethics Commission of our Hospital, and all participants consented to the study and for non-commercial use of their data.
Procedures
We collected data from the participants on the first to the third day of discharge using telephone interviews. The patients were aged from one month to 86 years and had tested positive for Omicron infection using quantitative polymerase chain reaction on samples from the respiratory tract. All patients were diagnosed with mild disease according to the ninth edition of the COVID-19 China Diagnosis and Treatment Guideline [5]. The questionnaire was designed by the research team based on the number of upper airway symptoms using the visual analogue scale (VAS). We also examined age, sex, vaccination status, general symptoms, and the cure period. For more details on the inclusion and exclusion criteria, refer to the Appendix (p1). The full list of symptoms queried is presented in the Appendix (p2–4).
Outcomes
The primary outcomes were the symptoms, general condition, cure period, and vaccination status. All outcome measures and assessment tools are listed in the Appendix (p3–4). The secondary outcome was the duration of upper airway symptoms from Omicron versus different vaccination statuses (zero, one, two, and three doses). The cure period was from definite diagnosis to the second nucleic acid-negative test.
Statistical analysis
Statistical analyses were performed using Microsoft Excel (Microsoft Corporation, Redmond, WA, USA) and GraphPad Prism 8 (GraphPad Software, San Diego, CA, USA).
Demographic characteristics are presented as means (SD) for continuous variables and percentages for categorical variables.
Clinical characteristics and upper airway symptom scores for different severity categories are shown. Participants were categorised into four vaccination statuses based on the number of doses of a COVID-19 vaccine they had received (zero, one, two, and three). For the comparison of the clinical characteristics and upper airway symptoms with different vaccination backgrounds, the Kruskal Wallis test, X2 test, Fisher’s exact test, or Mann-Whitney U test were used when appropriate.
All significance tests were two-sided, and a p-value of less than 0.05 was considered statistically significant unless stated otherwise.
Role of the funding source
The funder of the study had no role in the study design, data collection, data analysis, data interpretation, or writing of the manuscript.
Results
A total of 4284 patients with mild COVID-19 from the Omicron variant in Fangcang Shelter Hospitals (Changchun, China) were discharged between 10 March and 30 May 2022. In total, 3715 (86.72 %; 2056 males and 1659 females) participants were enroled in this study. The participants had a mean age of 38.63 (±13.97) years (range: one month to 86 years). Furthermore, the cure period ranged from three to 37 days, with a mean of 10.24±4.69 days (n = 3660). The vaccine uptake rate was 91.33 % (n = 3715), with 8.66 % (n = 3715), 4.58 % (n = 3715), 65.33 % (n = 3715), and 21.43 % (n = 3715) of the patients having received zero, one, two, and three doses, respectively ( Fig. 1).
Fig. 1.
Vaccine uptake rate, n = 3715.
The clinical symptom prevalence of Omicron infection includes upper airway symptoms, lower airway symptoms, gastrointestinal symptoms, and general symptoms. The incidence of upper airway symptoms, including throat and nasal symptoms, was 54.21 % (n = 3715). The incidence of lower airway symptoms was 25.60 % (n = 3715). The incidence of gastrointestinal symptoms was 10.87 % (n = 3715). The incidence of general symptoms was 55.26 % (n = 3715)( Fig. 2, Fig. 3; Table 1).
Fig. 2.
Four major symptoms of Omicron infection.
Fig. 3.
Incidence of the clinical symptoms of Omicron.
Table 1.
Prevalence of the clinical characteristics of Omicron.
| Total (n = 3715) | |
|---|---|
| Age, years | 38.63 ( ± 13.97) |
| Sex | |
| Male | 2056 |
| Female | 1659 |
| Length of hospital stay, days | 10.24 ± 4.69 |
| Upperairway symptoms | 2014/3715 (54.21 %) |
| Throat symptoms | 1836/3715 (49.42 %) |
| Dry cough | 1395/3715 (37.55 %) |
| Sore | 512/3715 (13.78 %) |
| Swallow sore | 156/3715 (4.20 %) |
| Dryness of throat | 448/3715 (12.06 %) |
| Itch | 251/3715 (6.76 %) |
| Foreign body sensation | 238/3715 (6.41 %) |
| Hoarseness | 135/3715 (3.63 %) |
| Buck | 6/3715 (0.16 %) |
| Dysphagia | 4/3715 (0.11 %) |
| Nasal symptoms | 746/3715 (20.08 %) |
| Congestion | 350/3715 (9.42 %) |
| Discharge | 338/3715 (9.10 %) |
| Sneeze | 98/3715 (2.64 %) |
| Itch | 26/3715 (0.70 %) |
| Dryness | 67/3715 (1.80 %) |
| Sore | 10/3715 (0.27 %) |
| Blood discharge | 23/3715 (0.62 %) |
| Loss of smell | 193/3715 (5.20 %) |
| Dysgeusia | 189/3715 (5.09 %) |
| Lower airway symptoms | 951/3715 (25.60 %) |
| Hemoptysis | 9/3715 (0.24 %) |
| Chest tight | 70/3715 (1.88 %) |
| Breathlessness | 61/3715 (1.64 %) |
| Spit | 901/3715 (24.25 %) |
| Grastrointestinal symptoms | 404/3715 (10.87 %) |
| Gastro-oesophageal reflux | 7/3715 (0.19 %) |
| Diarrhoea before treatment | 243/3715 (6.54 %) |
| Stomachache | 58/3715 (1.56 %) |
| Loss of appetite | 196/3715 (5.28 %) |
| The general symptoms | 2053/3715 (55.26 %) |
| Fever | 1742/3715 (46.89 %) |
| Headache | 273/3715 (7.35 %) |
| Tiredness | 231/3715 (6.22 %) |
| Powerless | 438/3715 (11.79 %) |
| Muscular soreness | 496/3715 (13.35 %) |
| Joints pain | 193/3715 (5.20 %) |
| Dysbasia | 3/3715 (0.08 %) |
| Sleep disturbances | 158/3715 (4.25 %) |
| mental confusion | 16/3715 (0.43 %) |
| hypomnesis | 30/3715 (0.81 %) |
| Alopecia | 19/3715 (0.51 %) |
| Lost weight | 22/3715 (0.59 %) |
| Paramenia | 41/1659 (2.47 %) |
Throat symptoms were the most common during Omicron infection (49.12 %, n = 3715). These included dry cough (37.55 %, n = 3715; severity from 1 to 10, VAS mean 3.19 ± 1.83, n = 1395), sore throat (13.78 %, n = 3715, severity from 1 to 10, VAS mean 3.58 ± 2.09, n = 512), sore throat on swallowing (4.20 %, n = 3715, severity from 1 to 10, VAS mean 4.49 ± 2.29, n = 156), dry throat (12.06 %, n = 3715, severity from 1 to 10, VAS mean 3.27 ± 1.76, n = 448), itchy throat (6.76 %, n = 3715, severity from 1 to 10, VAS mean 3.10 ± 1.67, n = 251), foreign body sensation (6.41 %, n = 3715, severity from 1 to 8, VAS mean 3.11 ± 1.29, n = 238), hoarseness (3.63 %, n = 3715, severity from 1 to 10, VAS mean 3.85 ± 2.17, n = 135), buck (0.16 %, n = 3715, severity from 1 to 7, VAS mean 3.00 ± 1.92, n = 6), and dysphagia (0.11 %, n = 3715, severity from 1 to 5, VAS mean is 3.00 ± 1.41, n = 4) ( Fig. 4, Fig. 5).
Fig. 4.
Incidence of throat symptoms.
Fig. 5.
VAS scores of throat symptoms.
Nasal symptoms were also common (20.08 %, n = 3751) and included congestion (9.42 %, n = 3715, severity from 1 to 10, VAS mean 3.55 ± 2.09, n = 351), discharge (9.10 %, n = 3715, severity from 1 to 10, VAS mean 3.08 ± 1.84, n = 338), sneezing (2.64 %, n = 3715, severity from 1 to 10, VAS mean 2.99 ± 1.95, n = 98), itchy nose (0.70 %, n = 3715, severity from 1 to 8, VAS mean 2.62 ± 1.47, n = 26), dry nose (1.80 %, n = 3715, severity from 1 to 8, VAS mean 3.75 ± 2.02, n = 67), sore nose (0.27 %, severity from 2 to 8, VAS mean 3.70 ± 2.33, n = 10), bloody discharge (0.62 %, n = 3715, severity from 1 to 7, VAS mean 2.78 ± 1.61, n = 23), loss of smell (5.20 %, n = 3715, severity from 1 to 10, VAS mean 5.57 ± 2.99, n = 193), and dysgeusia (5.09 %, severity from 1 to 10, VAS mean 4.86 ± 2.72, n = 189) ( Fig. 6, Fig. 7), respectively.
Fig. 6.
Incidence of nasal symptoms.
Fig. 7.
VAS scores of nasal symptoms.
The incidence of lower airway symptoms was 25.60 % (n = 3715) and included haemoptysis (0.24 %, n = 3715, severity from 1 to 7, VAS mean 2.78 ± 1.75, n = 9), chest tightness (1.88 %, n = 3715, severity from 1 to 9, VAS mean 3.69 ± 2.11, n = 70), breathlessness (1.64 %, n = 3715, severity from 1 to 8, VAS mean 3.11 ± 1.63, n = 61), and spit (24.25 %, n = 3715, severity from 1 to 9, VAS mean 2.85 ± 1.67, n = 901) ( Fig. 8, Fig. 9), respectively.
Fig. 8.
Incidence of lower airway symptoms.
Fig. 9.
VAS scores of lower airway symptoms.
The incidence of gastrointestinal symptoms was 10.87 % (n = 3715) and included gastroesophageal reflux (0.19 %, n = 3715, severity from 2 to 6, VAS mean 3.43 ± 1.18, n = 7), diarrhoea before treatment (6.54 %, n = 3715, severity from 1 to 8; VAS mean 2.78 ± 1.66; n = 243), stomach ache (1.56 %, n = 3715, severity from 1 to 8, VAS mean 2.47 ± 1.68, n = 58), and loss of appetite (5.28 %, n = 3715, severity from 1 to 9, VAS mean 3.74 ± 2.05, n = 196) ( Fig. 10, Fig. 11), respectively.
Fig. 10.
Incidence of gastrointestinal symptoms.
Fig. 11.
VAS scores of lower airway symptoms.
The incidence of general symptoms was 55.26 % (n = 3715) and included fever (46.89 %, n = 3715, mean temperature 38.31 ± 0.71 ℃, n = 1496), headache (7.35 %, n = 3715, severity from 1 to 10, VAS mean 3.66 ± 2.21, n = 273), tiredness (6.22 %, n = 3715, severity from 1 to 10, VAS mean 3.25 ± 1.86, n = 231), feeling powerless (11.79 %, n = 3715, severity from 1 to 10, VAS mean 3.38 ± 1.93, n = 438), muscular soreness (13.35 %, n = 3715, severity from 1 to 10, VAS mean 3.79 ± 2.05, n = 496), joint pain (5.20 %, n = 3715, severity from 1 to 9, VAS mean 3.51 ± 1.92, n = 193), dysbasia (0.08 %, n = 3715, severity from 3 to 8, VAS mean 5.00 ± 2.16, n = 3), sleep disturbances (4.25 %, n = 3715, severity from 1 to 8, VAS mean 4.26 ± 1.91, n = 158), mental confusion (0.43 %, n = 3715, severity from 1 to 8, VAS mean 3.69 ± 1.83, n = 16), hypomnesis (0.81 %, n = 3715, severity from 1 to 6, VAS mean 3.10 ± 1.56, n = 30), alopecia (0.51 %, n = 3715, severity from 1 to 8, VAS mean 3.16 ± 2.13, n = 19), weight loss (0.59 %, n = 3715, severity from 1 to 8, VAS mean 2.82 ± 2.25, n = 22), and paramenia (2.47 %, n = 1659, severity from 1 to 10, VAS mean 2.85 ± 2.53, n = 41) ( Fig. 12, Fig. 13), respectively.
Fig. 12.
Incidence of general symptoms.
Fig. 13.
VAS scores of the general symptoms.
Participants were categorised into four vaccination status groups in relation to whether they had received zero, one, two, or three vaccinations. We compared the severity of upper airway symptoms in Omicron among the different vaccination status groups (zero, one, two, and three doses). There were no differences among all the groups, but hoarseness, discharge, and dysphagia were more severe in the three dose group than that in the other groups ( Fig. 14 and Table 2).
Fig. 14.
Mean VAS scores of the upper airway symptoms in the four vaccination status groups. Zero, one, two, and three means that the patient had received zero, one, two, and three doses, respectively.
Table 2.
Comparison of the severity of upper airway symptoms in the four different vaccination status groups.
| 0 dose | 1 dose | 2 dose | 3 does | P value | |
|---|---|---|---|---|---|
| Dry cough | 3.06 ± 2.07 (n = 95) |
3.38 ± 1.79 (n = 47) |
3.15 ± 1.77 (n = 913) |
3.31 ± 1.90 (n = 340) |
0.4487 |
| Sore | 3.44 ± 2.02 (n = 25) |
3.95 ± 2.40 (n = 22) |
3.60 ± 2.09 (n = 337) |
3.51 ± 2.03 (n = 128) |
0.8223 |
| Swallow sore | 4.90 ± 2.39 (n = 10) |
4.86 ± 2.23 (n = 7) |
4.47 ± 2.30 (n = 106) |
4.36 ± 2.23 (n = 33) |
0.8914 |
| Dryness of throat | 2.64 ± 1.52 (n = 25) |
3.35 ± 1.68 (n = 20) |
3.26 ± 1.74 (n = 292) |
3.44 ± 1.85 (n = 111) |
0.2028 |
| Throat itch | 3.21 ± 1.52 (n = 14) |
3.86 ± 2.42 (n = 7) |
2.99 ± 1.59 (n = 148) |
3.20 ± 1.74 (n = 82) |
0.6084 |
| Foreign body sensation | 3.00 ± 1.35 (n = 12) |
3.88 ± 1.36 (n = 8) |
3.09 ± 1.25 (n = 164) |
3.07 ± 1.36 (n = 54) |
0.4368 |
| Hoarseness | 2.60 ± 0.80 (n = 5) |
3.83 ± 1.34 (n = 6) |
3.56 ± 1.90 (n = 81) |
4.56 ± 2.61 (n = 43) |
0.0082 |
| Buck | / | 7.00 (n = 1) |
2.00 ± 0.71 (n = 4) |
3.00 (n = 1) |
/ |
| Dysphagia | / | 3.00 (n = 1) |
3.00 ± 1.63 (n = 3) |
/ | / |
| Congestion | 2.92 ± 2.20 (n = 13) |
2.93 ± 1.34 (n = 15) |
3.51 ± 2.03 (n = 227) |
3.81 ± 2.26 (n = 95) |
0.2150 |
| Discharge | 1.92 ± 0.73 (n = 13) |
2.00 ± 0.77 (n = 10) |
3.11 ± 1.77 (n = 221) |
3.29 ± 2.09 (n = 94) |
0.0005 |
| Sneeze | 2.25 ± 0.43 (n = 4) |
1.67 ± 0.47 (n = 3) |
2.89 ± 1.77 (n = 66) |
3.52 ± 2.44 (n = 25) |
0.0671 |
| Nasal itch | / | 2.50 ± 1.50 (n = 2) |
2.56 ± 1.62 (n = 16) |
2.75 ± 1.09 (n = 8) |
/ |
| Dryness | 2.33 ± 2.56 (n = 6) |
3.00 (n = 1) |
3.82 ± 1.91 (n = 45) |
4.13 ± 1.89 (n = 15) |
/ |
| Nasal pain | / | / | 4.29 ± 2.55 (n = 7) |
2.33 ± 0.47 (n = 3) |
/ |
| Blood discharge | 2.00 (n = 1) |
/ | 3.06 ± 1.70 (n = 17) |
2.00 ± 1.10 (n = 5) |
/ |
| Loss of smell | 4.73 ± 2.99 (n = 11) |
4.83 ± 3.34 (n = 6) |
5.53 ± 2.89 (n = 125) |
5.92 ± 3.10 (n = 51) |
0.6218 |
| Dysgeusia | 4.08 ± 2.62 (n = 13) |
2.89 ± 1.29 (n = 9) |
4.96 ± 2.71 (n = 124) |
5.21 ± 2.81 (n = 43) |
0.0389 |
0 dose means patients received zero dose vaccinations, 1 dose means received one vaccinations, 2 dose means received two vaccinations, 3 dose means received three vaccinations.
Discussion
This study has reported the characteristics of clinical symptoms, especially upper airway symptoms, in patients with Omicron infection. The impact of different vaccination statuses on symptom severity was analysed. The sample size of this study was relatively limited in terms of symptom severity due to time and specific disease conditions, but it still has considerable practical value.
The clinical symptom features of Omicron infection were different from the Delta SARS-Cov-2 variant to some extent. Omicron belong to the single strand RNA virus, size 29.6 kb. Angiotensin converting enzyme 2 is the receptor as well as delta. Mortality rate is 0.01 %, but 2–4 % of delta. Compared to other variants, 34 different mutations of BA.1 variant in the spike glycoprotein, some of the mutations are predicted to enable immune escape. The spike protein of Omicron tends to use the alternative cathepsin L mediated entry rather than canonical TMPRSS2 pathway that may improves its ability to infect in upper airway, the relative infection ability was reduced due to lack of TMPRSS2 expressing cells of lower airway [6]. According to early government data from the United Kingdom, cold-like symptoms are the most commonly reported symptoms with the Omicron variant, followed by a runny nose, headache, fatigue, sneezing, and sore throat [7]. Upper airway symptoms are more common in those with Omicron than those with the Delta variant, although the mechanism remains unclear. Our study investigated upper airway symptoms, lower airway symptoms, gastrointestinal symptoms, and general symptoms, which were the most common clinical features of Omicron infection. Fever was the most common symptom (46.89 %). Upper airway symptoms, including nasal and throat symptoms, occurred in up to 54.12 % of cases, and dry cough (37.55 %) and sore throat (13.78 %) were the most common. In contrast to the earlier waves of SARS-CoV-2 infection, the incidence of olfactory symptoms was just 5.2 %; similar results were also reported by Menni [8]. The overall incidence of nasal symptoms was 20.08 %, which was lower than that of the lower airway (25.60 %) and general symptoms (55.26 %).
A South Korean study of 40 patients with Omicron revealed that sore throat (25%) and fever (20%) were the most common symptoms [9]. A report from South Africa purported that Omicron was generally “extremely mild,” with patients complaining of a scratchy throat rather than the usual complaints of a “sore throat”[10]. However, the conclusions of these studies are contradictory. In our study, fever (≥37.3 °C) remained the most common symptom, with a mean temperature of 38.3 °C in 1496 cases. Dry cough was the second highest, followed by a sore throat. The incidence of hoarseness (3.63 %, 135 cases) was not very high, and the mean VAS score was 3.85, indicating mild severity.
Early studies also suggested that Omicron infection is associated with a lower risk of hospitalisation, serious disease, and death [11]. Several studies have suggested a decrease in disease severity and a reduced risk of hospitalisation with Omicron [12], [13]. Our cohort included 3715 patients aged from one month to 86 years old. Thirty-eight symptoms were investigated, and no severe symptoms were observed according to the mean VAS score. All clinical symptoms were mild to moderate, and none of the patients died or developed serious disease. The swallow score had the highest score for throat symptoms, loss of smell was the highest in nasal symptoms, chest tightness in lower airway symptoms, loss of appetite in gastrointestinal symptoms, and dysbasia in general symptoms. In addition, the cure period ranged from three to 37 days, with a mean of 10.24 ± 4.69 days (cure period means from the date of definite diagnosis to cure, according to the National Health Commission of the People’s Republic of China). Considering all the patients in our study were from hospital shelters, the cure period might be shortened compared to self-management without medical knowledge. However, more data are needed to determine this.
Omicron infection results in milder symptoms than Delta; however, it is still unclear whether the reduced severity is caused by the station of the variant [14]. Nevertheless, the Omicron variant has been highly challenging for public health authorities worldwide due to its high transmission and capability to evade infection-blocking antibodies provoked by COVID-19 vaccines [15]. Some results have shown that after two doses of the SARS-CoV-2 vaccine, Omicron neutralisation is far less than Delta, and the third dose of the vaccine enhances the neutralisation of Omicron [16], [17]. In our study, the vaccine uptake rate was up to 91.33 % in patients diagnosed with Omicron infection, suggesting that there is no association between Omicron infection and COVID-19 vaccines. Various mutations present in the Omicron variant lead to immune evasion from vaccines. A Danish study including 599 cases showed that 83.1 % of cases were fully vaccinated or received full vaccination plus a booster dose [18]. Therefore, it appears that people are still susceptible to Omicron infection even if they have received vaccination against COVID-19. Furthermore, in our study, the two vaccine dose rates were the highest (65.33 %, n = 3715) among the patients diagnosed, which is consistent with the general vaccination situation in China [19].
We also analysed the association between the severity of upper airway symptoms and vaccination status. Although the data revealed that the Omicron variant more easily evaded infection-blocking antibodies provoked by COVID-19 vaccines, some studies reported that the serum neutralisation assay found that the escape was incomplete, and patients who were vaccinated showed relatively high neutralisation titres against Omicron [20], [21]. Vaccines were found to be highly effective in preventing COVID-19-associated disease severity related to Omicron, but three doses were required [22]. However, other studies have reported contrasting results. One study suggested that primary immunisation with a vaccine provided limited protection against symptomatic disease caused by the Omicron variant [23]. A neutralising activity study of sera from convalescent and double-vaccinated participants was undetectable or very low against Omicron [24]. Vaccinations may be ineffective against the Omicron variant of SARS-CoV-2, and double immunisation with BNT162b2 might not adequately protect against severe disease from this variant [25]. Our results suggest that vaccination might be ineffective in preventing upper airway symptoms caused by Omicron.
Collectively, our results suggested that upper airway symptoms are one of the most common clinical features of the SARS-Cov-2 Omicron variant; fever was the most common symptom, followed by a mild dry cough and mild sore throat. There was no association between Omicron infection and COVID-19 vaccines, and vaccination might be ineffective in preventing upper airway symptoms caused by Omicron. The clinical implication of our findings is that to provide reference for diagnosis before laboratory-confirmed Omicron, and provide a basis for the development of symptomatic treatment strategies.
CRediT authorship contribution statement
Jichao Sha, Cuida Meng, Jing Sun and Dongdong Zhu conceived the idea of the study, Cuida Meng and Jing Sun are co-first authors; Jichao Sha and Dongdong Zhu searched literature and designed this study. Cuida Meng and Jing Sun collected and analysed date, Liwei Sun analysed the data and pre; Rui Gu, Junzhi Liu and Xuewei Zhu interpreted the results; Sha Jichao wrote the paper; all authors discussed the results and revised the manuscript.
We all declare no competing interests.
Conflict of interest
The authors declared that they have no potential conflicts of interest.
Acknowledgements
This work was supported by grants from the National Natural Science Foundation of China (82071016,81870701), the Programme National Natural Science Foundation of Jilin Provincial (20200201600JC，20200201411JC，20200201200JC), Jilin Province Health Science and Technology Talent Project (2019scz004, 2020scz24). We thank all staff of this study team at China-Japan Union Hospital of Jilin University, and all staff in the Tongyuan and Yongshilu Fangcang shelter hospitals who all be from China-Japan Union Hospital.
Footnotes
Supplementary data associated with this article can be found in the online version at doi:10.1016/j.jiph.2023.01.013.
Appendix A. Supplementary material
Supplementary material
.
References
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