The Recombinant COVID-19 (XBB) Trimer Protein Vaccine (Sf9 Cell) developed by WestVac Biopharma Co., Ltd. is a monovalent modified vaccine designed against Omicron XBB.1.5.

This is a multi-center, randomized, double-blind, placebo-controlled phase 3 clinical study with two cohorts, i.e. the immuno-bridging observational cohort and the efficacy observational cohort, aims to evaluate the efficacy, safety, and immunogenicity of booster vaccination with Recombinant COVID-19 (XBB) Trimer Protein Vaccine (Sf9 Cell) for the prevention of SARS-CoV-2 infection in a population of 18 years of age and older.

Inclusion Criteria:

1. Subjects aged 18 years and above, including those with underlying diseases or immunocompromised.
2. Basic or booster vaccination with COVID-19 vaccine ≥3 months.
3. No history of SARS-CoV-2 infection history within 3 months, or never infected.
4. Have the ability to understand research procedures, with informed consent, voluntarily sign informed consent form, and be able to comply with the requirements of clinical study protocol.

Exclusion Criteria:

1. Axillary temperature ≥37.3℃.
2. SARS-CoV-2 antigen or nucleic acid screening positive during the screening period.
3. Anti-SARS-CoV-2 IgM antibody screening positive during the screening period.
4. It is in the advanced stage of malignant tumor and the disease control is unstable.
5. Female pregnancy (pregnancy test results are positive), lactation period.
6. Suffering from serious cardiovascular diseases, such as arrhythmia, conduction block, myocardial infarction, heart failure etc.; suffering from severe hypertension that can not be controlled by drugs.
7. Suffering from other serious chronic conditions such as uncontrolled asthma, diabetes, chronic obstructive pulmonary disease, pulmonary embolism, chronic kidney disease requiring dialysis, cirrhosis of the liver, convulsions, epilepsy and other neurological/psychiatric conditions.
8. Have been diagnosed with congenital or acquired immunodeficiency, HIV infection (including anti-HIV antibody positive during the screening period).
9. People who are allergic to any component of the investigational vaccine and have a history of severe allergies or vaccine allergic reactions in the past.
10. Congenital or acquired angioedema/neuropathic edema.
11. Asplenia or functional asplenia.
12. Thrombocytopenia or other clotting disorders (which may cause intramuscular injection contraindications).
13. Received another investigational drug within 1 month prior to receiving the investigational vaccine.
14. Received subunit or inactivated vaccine within 14 days prior to receiving the investigational vaccine, or received live attenuated vaccine within 1 month.
15. Fertile female subjects did not use effective contraception within 1 month prior to enrollment.
16. Fertile female and male subjects have pregnancy plans and sperm/egg donation plans from the screening period to 3 months after vaccination.
17. Medical, psychological, social, or other conditions that, in the investigator's judgment, are inconsistent with the protocol or affect the subject's signing of informed consent.