A Trial Evaluate the Immunogenicity and Safety of Recombinant COVID-19 Omicron-Delta Variant Vaccine (CHO Cell)

Inclusion Criteria: * Age eligible for observation in this clinical trial: adults aged 18 years and above * Subjects voluntarily participate in this study, sign informed consent, provide legal identification, and understand and comply with the requirements of the test protocol * More than 4 months after the completion of the whole course of recombinant novel coronavirus protein vaccine (CHO cell) basic immunization or more than 4 months after the completion of the novel coronavirus mRNA vaccine basic immunization * Female and male participants of childbearing age took effective contraception during the study period Exclusion Criteria: * Prior history of severe allergy to any vaccine or to any component of the test vaccine, including aluminum preparation, such as anaphylactic shock, allergic laryngeal edema, purpura, thrombocytopenic purpura, local allergic necrosis reaction (Arthus reaction), dyspnea, angineurotic edema, etc.; * Suspected or confirmed fever (axillary temperature ≥37.3℃/ mouth temperature ≥37.5℃) within 72 hours before enrollment, or armpit temperature ≥37.3℃/ mouth temperature ≥37.5℃ on the day of enrollment; * Confirmed cases of COVID-19 infection, asymptomatic infected persons or positive nucleic acid test history of COVID-19; * Uncontrolled lymphoproliferative disease, unremission stage of aplastic anemia, active stage of primary immune thrombocytopenia (ITP), uncontrolled stage of coagulation disease, etc. * a history of congenital or acquired immunodeficiency or autoimmune disease; Absence of spleen, or history of splenic surgery, trauma, or immunomodulator treatment within 6 months, such as immunosuppressive dose of glucocorticoids (dose reference: equivalent to prednisone 20mg/ day, over a week); Or monoclonal antibodies; Or thymosin; Or interferon; But topical use (such as ointments, eye drops, inhalants or nasal sprays) is permitted; * Subunit vaccine and inactivated vaccine should be administered within 14 days before vaccination, and live attenuated vaccine should be administered within 30 days before vaccination; * Patients with malignant tumors who are undergoing chemotherapy, radiotherapy or immunotherapy before and after surgery; Patients with organ transplant status; * People with uncontrolled epilepsy and other progressive neurological diseases (e.g. Transverse myelitis, Guillain-Barre syndrome, demyelinating diseases, etc.); * Patients with acute disease, or acute episodes of chronic disease, or uncontrolled severe chronic disease, such as medically uncontrolled hypertension (systolic blood pressure ≥150mmHg and/or diastolic blood pressure ≥100mmHg); * lactating or pregnant women; * The investigator believes that the subject has any disease or condition that could put the subject at risk; The subject is unable to complete the trial as required by the protocol, and there are circumstances that interfere with the assessment of vaccine response.