Inclusion Criteria:

- Age range: healthy population aged ≥18;

- Judged by the investigator that the health condition is well after inquiry and
physical examination;

- Cohort 1: participants vaccinated with ≥2 doses of inactivated COVID-19 vaccines for
≥6 months since the last dose of vaccination; Cohort 2: participants vaccinated with
≥2 doses of mRNA COVID-19 vaccines for ≥6 months since the last dose of vaccination;

- Be able and willing to complete all prescribed study schedules during the whole
study period;

- The participant himself/herself is able and willing to understand study procedures,
sign the informed consent form voluntarily after informed consent and comply to
requirements of the study protocol.

Exclusion Criteria:

- Symptomatic and suspected COVID 19 infection positive ;

- Urine pregnancy test is positive; Women of childbearing age who have positive urine
pregnancy test, who are pregnant, lactating, or women who have planned pregnancy
within 6 months;

- Auxiliary temperature before vaccination is ≥37.3℃ (tympanic/forehead temperature
≥37.8℃);

- Previous allergy history of vaccine vaccination (such as acute allergic reaction,
urticaria, skin eczema, dyspnea, angioneurotic edema or abdominal pain, etc.) or
allergy to known components of COVID-19 vaccine;

- Have a history of hospital-diagnosed thrombocytopenia or other coagulation
disorders;

- With known immunological impairment or compromised immunological function diagnosed
by the hospital;

- Received whole blood, plasma and immunoglobulin therapy within 1 month;

- Known or suspected of suffering from the following diseases: acute or chronic active
respiratory diseases, severe cardiovascular diseases [cardiopulmonary failure,
hypertension uncontrollable by drugs (systolic blood pressure ≥ 150 mmHg and/or
diastolic blood pressure ≥ 95 mmHg)], acute infection, active phase of chronic
disease, liver and kidney diseases, severe diabetes, malignant tumor, infectious
skin diseases or severe skin allergy, HIV infection, etc. (Examination report can be
provided)

- Received live attenuated vaccine within one month before vaccination;

- Received inactivated vaccine within 14 days before vaccination;

- Other contraindications related to vaccination that investigators believe.