Inclusion Criteria:  Healthy subjects over 18 years old, and can provide vaccination information to prove that they have completed 2 doses of inactivated novel coronavirus vaccine (BBIBP-CorV) within the past 3-9 months; The subjects voluntarily participate in the research, sign the informed consent form, and can provide valid identification, understand and comply with the requirements of the study protocol; Female subjects of childbearing age agree to use effective contraception from the start of the study to 2 months after vaccination.  Exclusion Criteria:  Suspected or confirmed fever (fever ≥38.5℃) within 72 hours before enrollment, or axillary body temperature ≥37.3℃ on the day of enrollment; Diastolic blood pressure ≥ 100 mmHg and/or systolic blood pressure ≥ 160 mmHg without or after drug control; Have a history of previous infection with new coronary pneumonia or a positive nucleic acid test history; Those who currently suffer from the following diseases: 1.Thrombocytopenia, any coagulation disorder, or receiving anticoagulant therapy, etc.; 2.History of congenital or acquired immunodeficiency or autoimmune disease; asplenia, or history of spleen surgery, trauma, or treatment with immunomodulatory agents within 6 months, such as: immunosuppressive doses of glucocorticoids (dose reference: equivalent or prednisone 20mg/day for more than one week); or monoclonal antibody; or thymosin; or interferon, etc.; 3.Those suffering from acute infectious diseases or using antipyretic/analgesic/antiallergic drugs within 3 days before enrollment, or acute exacerbation of chronic diseases; 4.Cancer patients (except basal cell carcinoma) who have been off treatment for less than 6 months; 5.Serious chronic diseases such as congenital heart disease, severe liver and kidney disease, severe diabetes (with complications) that may interfere with the conduct or completion of the study; 6.Active tuberculosis, viral hepatitis patients with obvious liver damage (excluding virus carriers) and/or HIV-positive or syphilis-specific antibody-positive; Previous history of severe hypersensitivity to any vaccine, or severe hypersensitivity history to any component of the investigational vaccine, including aluminum preparations, such as: anaphylactic shock, allergic laryngeal edema, anaphylactoid purpura, thrombocytopenic purpura, dyspnea, vascular nerve edema, etc.; Administer subunit vaccine and inactivated vaccine within 14 days before the trial vaccine, and receive live attenuated vaccine within 28 days; Received blood or blood-related products, including immune globulin, within 3 months prior to screening; or planned use within 6 months after study initiation to full vaccination; In addition to completing 2 doses of inactivated novel coronavirus vaccine within the past 3-9 months, participating in other COVID-19 related clinical trials; Pregnant women (including women of childbearing age with positive urine pregnancy test); Investigators believe that the presence of any disease or condition in the subject may put the subject at unacceptable risk; the subject cannot meet protocol requirements; interfere with the assessment of vaccine response, etc.