Inclusion Criteria:

1. Healthy participants aged 18 years and older who have completed the second dose of
2-dose regimen of SARS-CoV-2 Inactivated Vaccine in the past 6 (±1) months;

2. Voluntarily participate in the study and sign the informed consent form, who can
provide valid ID and follow the study protocol requirement;

3. In the past 14 days, no history of high or medium risk of the epidemic, overseas
travel history or residence history; no history of contact with confirmed,
asymptomatic or suspected COVID-19 cases; no history of contact with the persons
from high- and medium-risk epidemic areas or contact patients with fever or
respiratory symptoms; and those who are not in isolation period.

4. Males of reproductive potential and females of childbearing potential voluntarily
agree to take effective and acceptable contraceptive methods from the signing of
informed consent form to 3 months after vaccination.

Exclusion Criteria:

1. Confirmed COVID-19 cases, or positive for SARS-CoV-2 test by RT-PCR. 2. History of
previous SARS infection. 3. History of severe allergy to any vaccine or any
ingredient of the vaccine including aluminum adjuvant, e.g., anaphylactic shock,
allergic laryngeal edema, allergic purpura, thrombocytopenic purpura, local allergic
necrosis reaction (Arthus reaction), dyspnea, angioedema, etc.

4. People who currently suffer from the following diseases:

1. Symptoms related to acute respiratory infections (such as: sneezing, nasal
congestion, runny nose, cough, sore throat, loss of taste, chills, shortness of
breath, etc.)

2. Patients with thrombocytopenia, any coagulation dysfunction, or receive
anticoagulant treatment, etc.

3. Patients with congenital or acquired angioedema/neuroedema;

4. A history of congenital or acquired immunodeficiency or autoimmune disease (except
for mild psoriasis, controllable autoimmune thyroid disease, vitiligo, or stable
celiac disease that does not require immunosuppressive or immunomodulatory therapy);
no spleen , or history of spleen surgery, history of trauma, or treatment with
immunomodulators within 6 months, such as: glucocorticoid with the dose causing
immunosuppressive (dose reference: equivalent to prednisone 20mg/day, more than one
week); or monoclonal antibody ; or thymosin; or interferon, etc.; but local
medication (such as ointment, eye drops, inhalation or nasal spray) is allowed.

5. Patients with active tuberculosis, viral hepatitis, human immunodeficiency virus or
syphilis infection.

6. Patients with acute diseases, or acute attacks of chronic diseases, or uncontrolled
severe chronic diseases: history of chronic respiratory diseases (including moderate
to severe asthma, COPD, pulmonary fibrosis), hypertension that cannot be controlled
by drugs (systolic blood pressure ≥150mmHg) And/or diastolic blood pressure
≥100mmHg), history of severe cardiovascular disease (including heart failure,
coronary artery disease, cardiomyopathy), history of chronic kidney disease, history
of cancer (except for basal cell carcinoma), diabetes (unsatisfied blood sugar
control or diabetes related serious complications).

5. Received inactivated vaccines or any subunit vaccines within 14 days before the
vaccination and attenuated live vaccine within 28 days before the vaccination.

6. Injection of immunoglobulin and/or other blood products within 3 months before the
administration of study vaccine; or with the plan to use such product within 6 month
after immunization.

7. Pregnant (including positive urine pregnancy test for women of childbearing age) or
breastfeeding women. Or women or their partners who have a pregnancy plan within 3
months after the trial vaccination.

8. Have participated in or are participating in other COVID-19 related clinical trials,
or are participating in other drug clinical trials; 9. Those considered by the
investigator as inappropriate to participate in the study.