Inclusion Criteria:

1. volunteers aged 18 years and above at the time of screening;

2. informed consent obtained from volunteers and volunteers/witnesses able to sign the
informed consent form;

3. an interval of ≥3 months from the last COVID-19 or influenza vaccination;

4. an interval of ≥ 3 months from the last respiratory viral infection such as COVID-19
or Influenza virus occurs; 5.1 cohort 1：novel coronavirus virus antigen-positive and
within 48 hours of onset of symptoms of infection; 5.2 cohort 2：influenza virus
antigen-positive and within 48 hours of onset of symptoms of infection; 5.3 cohort
3：novel coronavirus and influenza virus antigen-negative, no febrile symptoms, and
no symptoms of viral or bacterial respiratory infections.

Exclusion Criteria:

1. known or suspected concomitant more serious and medically unstable disease in the
judgment of the investigator, including: respiratory disease, tuberculosis, acute
infections or active chronic disease, hepatic or renal disease, cardiovascular
disease (cardiorespiratory failure), hypertension (systolic blood pressure ≥160
mmHg, diastolic blood pressure ≥100 mmHg), malignant tumors, infectious or allergic
skin diseases, and the presence of HIV infection;

2. Absence of spleen or functional absence of spleen;

3. immunosuppressive therapy, anti-allergy therapy, cytotoxic therapy, inhaled
corticosteroids (excluding corticosteroid spray therapy for allergic rhinitis, and
superficial corticosteroid therapy for acute uncomplicated dermatitis) within the
past 6 months;

4. Received blood products within the past 3 months;

5. has received other vaccines or investigational drugs within the past 1 month;

6. is receiving anti-tuberculosis treatment;

7. In the judgment of the investigator, due to a variety of medical, psychological,
social, or other conditions that are contrary to the trial protocol or that affect
the signing of informed consent by the volunteer.