Popular title: Clinical study of Omicron BA.4/5-Delta strain recombinant novel coronavirus protein vaccine (CHO cells).

Purpose of the study: Main objectives: To evaluate the immunogenicity and safety of Omicron BA.4/5-Delta strain recombinant novel coronavirus protein vaccine (CHO cells) against the new coronavirus prototype strain and Omicron variant (XBB, BA.5, BF.7) after receiving 2 doses according to different immunization schedules in people aged 18 years and older. Secondary purposes: To evaluate the immune persistence of Omicron BA.4/5-Delta recombinant novel coronavirus protein vaccine (CHO cells) against the new coronavirus prototype strain and Omicron variant (XBB, BA.5, BF.7) after receiving 2 doses according to different immunization schedules in people aged 18 years and older.

Overall design: Studies were randomized, double-blind, active-controlled study design.

Study group: There were 160 participants aged 18 years and older, including 80 people aged 60 years and older.

Study group：Among them, 80 subjects were from the "randomized, double-blind, active-controlled clinical study to evaluate the immunogenicity and safety of Omicron BA.4/5-Delta strain recombinant novel coronavirus protein vaccine (CHO cells) in people aged 18 years and older, protocol number: LKM-2023-NCV-02", 40 cases in the study group and 40 cases in the control group, and completed the second dose of vaccine at the 6th month visit to observe immunogenicity and safety. The remaining 80 subjects were randomly blinded to the 1:1 ratio into the research group and the control group and received 2 doses of the experimental vaccine according to the 0-1-month procedure to observe immunogenicity and safety.

Inclusion Criteria:

1. Be 18 years of age or older at the time of signing the informed consent form.
2. The subject himself voluntarily participates in the study, signs the informed consent form, and can provide legal identification, understand and comply with the requirements of the research protocol.
3. More than 6 months after completing the basic immunization or booster immunization of the new coronavirus vaccine.
4. Female subjects of childbearing age and male subjects who were able to use effective contraception during the study.

Exclusion Criteria:

Participants were not eligible for study if they had any of the following:

1. Previous history of severe allergy to any vaccine, or history of severe allergy to any component of the study vaccine, including aluminum preparations, such as: anaphylactic shock, allergic laryngeal edema, Henoch-Schönlein purpura, thrombocytopenic purpura, dyspnea, angioedema, allergic constitution (such as allergy to two or more drugs, food or pollen), etc.
2. fever (axillary body temperature≥ 37.3°C) within 72 hours before enrollment, or axillary body temperature ≥ 37.3°C on the day of enrollment.
3. Patients infected with the new coronavirus within 3 months before enrollment (asymptomatic infection or positive nucleic acid or antigen test of the new coronavirus).
4. Patients with aplastic anemia that has not been relieved, primary immune thrombocytopenia (ITP) active period, and uncontrolled coagulation diseases.
5. history of congenital or acquired immunodeficiency or autoimmune disease; no history of spleen or spleen surgery or trauma; or receive immunomodulators within 6 months, such as corticosteroids in immunosuppressant doses (dose reference: equivalent to prednisone 20 mg/day for more than one week); or monoclonal antibodies; or thymus peptide; or interferon, etc.; However, topical medications (such as ointments, eye drops, inhalers, or nasal sprays) are allowed; Lymphoproliferative disorders are not controlled.
6. Non-live vaccine ≤ 14 days before vaccination and live attenuated vaccine 30 days before ≤vaccination.
7. Patients with malignant tumors who are undergoing chemotherapy, radiotherapy, immunotherapy, etc. before and after surgery, Patients in the state of organ transplantation.
8. Those suffering from uncontrolled epilepsy and other progressive neurological diseases (such as transverse myelitis, Guillain-Barre syndrome, demyelinating diseases, etc.).
9. Patients with acute diseases, or acute exacerbations of chronic diseases, or uncontrolled severe chronic diseases, such as hypertension that cannot be controlled by drugs (systolic blood pressure ≥ 160mmHg and/or diastolic blood pressure ≥100mmHg).
10. Lactating women or pregnant women; The investigator believes that the participant has any disease or condition that would put the participant at risk, the participant cannot complete the study as required by the protocol, and there are circumstances that interfere with the assessment of vaccine response.