The purpose of this study is to evaluate the immunogenicity and safety of the recombinant novel coronavirus vaccine (CHO cells) after the booster immunization. It is planned to screen 300 subjects of 18 years old and above who have completed the basic immunization of recombinant novel coronavirus vaccine (CHO cells), to evaluate the immunogenicity and safety of the booster immunization of 6 months (window period ± 1 month) after the basic immunization. Investigate the geometric mean titer (GMT), GMI and 4 times growth rate of SARS-CoV-2 neutralizing antibody and RBD protein binding antibody 14 days, 30 days, and 6 months after booster vaccination; the incidence of all AEs within 1 month after the booster vaccination, the incidence of all serious adverse events (SAE) within 6 months after the booster vaccination.

This study adopts an open experimental design. It is planned to screen 300 subjects of 18 years old and above who have completed the basic immunization of recombinant novel coronavirus vaccine (CHO cells), to evaluate the immunogenicity and safety of the booster immunization of 6 months (window period ± 1 month) after the basic immunization.

Immunogenicity observation: the geometric mean titer (GMT), GMI and 4 times growth rate of SARS-CoV-2 neutralizing antibody and RBD protein binding antibody 14 days, 30 days, and 6 months after booster vaccination.

Safety observation:

1. All adverse events (AE) were collected within 30 minutes after the booster immunization, all AEs (including both solicited and unsolicited AEs) 0-7 days after the booster immunization, and all AEs (unsolicited AEs) 8-30 days after the booster immunization.

   Solicited AE (the following events occurring within 7 days of vaccination) :

   Adverse events at the inoculation site (local) : pain, pruritus, redness, swelling, rash, induration; Non-inoculated site (systemic) adverse events: fever, headache, fatigue, diarrhea, nausea, vomiting, muscle pain (non-inoculated site), acute allergic reactions, cough.

2. All SAEs were collected within 6 months after the booster immunization.

Inclusion Criteria:

• Subjects of 18 years old and above who has completed basic immunization with recombinant novel coronavirus vaccine (CHO cells) since 6 months (window period ± 1 month);
• The subjects voluntarily participate in the study, sign an informed consent form, and can provide valid identification, understand and comply with the requirements of the trial protocol;
• Female subjects of childbearing age agree to take effective contraceptive measures from the start of the study to 1 month after vaccination.

Exclusion Criteria:

• A confirmed case of novel coronavirus infection or asymptomatic infection or a history of positive novel coronavirus nucleic acid test;
• Patients with uncontrolled lymphoproliferative diseases, unresolved aplastic anemia, active primary immune thrombocytopenia (ITP), uncontrolled coagulopathy, etc;
• Patients with malignant tumors before and after surgery, patients undergoing chemotherapy, radiotherapy, immunotherapy, etc.; patients with organ transplantation status;
• People with uncontrolled epilepsy and other serious neurological diseases (such as transverse myelitis, Guillain-Barre syndrome, demyelinating diseases, etc.);
• Suffering from acute diseases, or acute attacks of chronic diseases, or uncontrolled severe chronic diseases, such as hypertension that cannot be controlled by drugs (systolic blood pressure ≥150mmHg and/or diastolic blood pressure ≥100mmHg);
• Previous history of severe allergies to any vaccine, or history of severe allergies to any component of the test vaccine, including aluminum preparations, such as: anaphylactic shock, allergic laryngeal edema, allergic purpura, thrombocytopenic purpura, dyspnea, vascular nerve Sexual edema, etc;
• Women who are breastfeeding or pregnant;
• In addition to completing the recombinant novel coronavirus vaccine (CHO cell) within the past 7 months, has participated or is participating in other COVID-19 related clinical trials;
• Investigators believe that any disease or condition may put the subject at an unacceptable risk; the subject cannot meet the requirements of the protocol; the situation that interferes with the assessment of the vaccine response.