Recombinant SARS-CoV-2 Fusion Protein Vaccine (V-01) Booster Study

Inclusion Criteria: Participants are eligible to be included in the study only if all of the following criteria apply: 1. Voluntarily participate in the study and sign the informed consent form. 2. Adults aged 18 years and older at time of consent, male or female. 3. Able to and willing to comply with study procedure based on the assessment of the investigator. 4. Participants who have completed the second dose of 2-dose regimen of inactive vaccination (BBIBP-CorV or CoronaVac) against SARS-CoV-2 in the past 3-6 months (Note: Participants who received mixed vaccination of BBIBP-CorV and CoronaVac will not be enrolled). 5. Healthy participants or participants with pre-existing stable medical conditions (A stable medical condition is defined as a disease not requiring significant change in therapy or hospitalization for worsening disease within 3 months before enrollment). 6. 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; and a female participant of childbearing potential should have a negative pregnancy test at screening and on the day of vaccination (day 0). Female participants of non-childbearing potential may be enrolled in the study. Non-childbearing potential is defined as surgically sterile (history of bilateral tubal ligation, bilateral oophorectomy, hysterectomy) or postmenopausal (defined as amenorrhea for ≥ 12 consecutive months prior to screening without an alternative medical cause). Exclusion Criteria: Participants are excluded from the study if any of the following criteria apply: 1. History of previous COVID-19 infection. 2. Positive for SARS-CoV-2 test by RT-PCR during screening period (Note: Participants can be enrolled in the study and receive the investigational product without waiting for the report of the SARS-CoV-2 test by RT-PCR). 3. History of severe acute respiratory syndrome (SARS), Middle East respiratory syndrome (MERS), and other human coronavirus infections or diseases. 4. History of severe allergy to any vaccine, e.g., acute allergic reactions, urticaria, skin eczema, dyspnea, angioneurotic edema or abdominal pain etc., or be allergic to any components of V-01. 5. Any confirmed or suspected immunosuppression or immunodeficiency condition known from medical history, including human immunodeficiency virus (HIV) infection, asplenia. 6. Serious or uncontrolled cardiovascular diseases, nervous system disorders (e.g., Guillain-Barre syndrome), blood and lymphatic system disorders, immune system disorders, hepatorenal disorders, respiratory system disorders (e.g., active tuberculosis, pulmonary fibrosis), metabolic and skeletal systems disorders or malignant tumors (except for skin basal cell carcinoma or in situ carcinoma of uterine cervix that has been cured for more than 5 years). 7. Hereditary hemorrhagic tendency or coagulation dysfunction, or a history of thrombosis or hemorrhagic disease, or requirement of continuous use of anticoagulants. 8. Prior use of any medication to prevent COVID-19 within 1 week before signing the informed consent form (except for previous vaccines, BBIBP-CorV or CoronaVac), e.g., use of antipyretics without pyrexia and any other symptoms. 9. Received attenuated live vaccine within 28 days before the vaccination or any other vaccines (licensed or investigational) within 14 days before the vaccination. 10. Has participated in an interventional clinical study within 1 months prior to the day of vaccination. 11. Injection of immunoglobulin and/or other blood products within 3 months before the administration of study vaccine. 12. Long-term use (continuous use \> 14 days) of glucocorticoids (≥ 10 mg/day of prednisone or its equivalent dose) or other immunosuppressive agents within 6 months before signing the informed consent form; however, enrollment is allowed for the following conditions: inhaled or topical use of topical steroids, or short-term use (treatment course ≤ 14 days) of oral steroids. 13. Pregnant or breastfeeding women. 14. Planning to donate blood during the study period. 15. Suspected or known alcohol or drug dependence. 16. History of severe psychiatric disorders which may affect study participation. 17. Planning to permanently move from the local area before study completion or leave the local area for a long time during the period of study visits, so that the scheduled visits cannot be followed. 18. Those considered by the investigator as inappropriate to participate in the study.