* history of sars-cov-2 infection; * any serious adverse reactions that are causally related to vaccination during the primary immunization of the previous inactivated sars-cov-2 vaccine; * severe allergic reactions after primary immunization (including urticaria/rash within 30 minutes after vaccination); * autoimmune disease or immunodeficiency / immunosuppression; * severe chronic diseases, severe cardiovascular diseases, hypertension and diabetes that cannot be controlled by drugs, liver or kidney diseases, malignant tumors, etc; * severe neurological disease (epilepsy, convulsions or convulsions) or mental illness; * immunosuppressive therapy, cytotoxic therapy, inhaled corticosteroids (excluding allergic rhinitis corticosteroid spray therapy, acute noncomplicated dermatitis superficial corticosteroid therapy) within 6 months before primary immunization and before booster immunization; * already pregnant or are breastfeeding, planning to get pregnant (according to subjects' self-report and urine pregnancy test results) * receipt of attenuated live vaccines within 14 days prior to booster vaccination; * receipt of inactivated or subunit vaccines within 7 days prior to booster vaccination; * acute diseases or acute exacerbation of chronic diseases within 7 days prior to booster vaccination; * axillary temperature \>37.0°c prior to booster vaccination; * according to the investigator's judgment, the subject has any other factors that are not suitable for participating in the clinical trial

* history of sars-cov-2 infection; * any serious adverse reactions that are causally related to vaccination during the primary immunization of the previous inactivated sars-cov-2 vaccine; * severe allergic reactions after primary immunization (including urticaria/rash within 30 minutes after vaccination); * autoimmune disease or immunodeficiency / immunosuppression; * severe chronic diseases, severe cardiovascular diseases, hypertension and diabetes that cannot be controlled by drugs, liver or kidney diseases, malignant tumors, etc; * severe neurological disease (epilepsy, convulsions or convulsions) or mental illness; * immunosuppressive therapy, cytotoxic therapy, inhaled corticosteroids (excluding allergic rhinitis corticosteroid spray therapy, acute noncomplicated dermatitis superficial corticosteroid therapy) within 6 months before primary immunization and before booster immunization; * already pregnant or are breastfeeding, planning to get pregnant (according to subjects' self-report and urine pregnancy test results) * receipt of attenuated live vaccines within 14 days prior to booster vaccination; * receipt of inactivated or subunit vaccines within 7 days prior to booster vaccination; * acute diseases or acute exacerbation of chronic diseases within 7 days prior to booster vaccination; * axillary temperature \>37.0°c prior to booster vaccination; * according to the investigator's judgment, the subject has any other factors that are not suitable for participating in the clinical trial

history of sars-cov-2 infection; any serious adverse reactions that are causally related to vaccination during the primary immunization of the previous inactivated sars-cov-2 vaccine; severe allergic reactions after primary immunization (including urticaria/rash within 30 minutes after vaccination); autoimmune disease or immunodeficiency / immunosuppression; severe chronic diseases, severe cardiovascular diseases, hypertension and diabetes that cannot be controlled by drugs, liver or kidney diseases, malignant tumors, etc; severe neurological disease (epilepsy, convulsions or convulsions) or mental illness; immunosuppressive therapy, cytotoxic therapy, inhaled corticosteroids (excluding allergic rhinitis corticosteroid spray therapy, acute noncomplicated dermatitis superficial corticosteroid therapy) within 6 months before primary immunization and before booster immunization; already pregnant or are breastfeeding, planning to get pregnant (according to subjects' self-report and urine pregnancy test results) receipt of attenuated live vaccines within 14 days prior to booster vaccination; receipt of inactivated or subunit vaccines within 7 days prior to booster vaccination; acute diseases or acute exacerbation of chronic diseases within 7 days prior to booster vaccination; axillary temperature >37.0°c prior to booster vaccination; according to the investigator's judgment, the subject has any other factors that are not suitable for participating in the clinical trial

history of sars-cov-2 infection; any serious adverse reactions that are causally related to vaccination during the primary immunization of the previous inactivated sars-cov-2 vaccine; severe allergic reactions after primary immunization (including urticaria/rash within 30 minutes after vaccination); autoimmune disease or immunodeficiency / immunosuppression; severe chronic diseases, severe cardiovascular diseases, hypertension and diabetes that cannot be controlled by drugs, liver or kidney diseases, malignant tumors, etc; severe neurological disease (epilepsy, convulsions or convulsions) or mental illness; immunosuppressive therapy, cytotoxic therapy, inhaled corticosteroids (excluding allergic rhinitis corticosteroid spray therapy, acute noncomplicated dermatitis superficial corticosteroid therapy) within 6 months before primary immunization and before booster immunization; already pregnant or are breastfeeding, planning to get pregnant (according to subjects' self-report and urine pregnancy test results) receipt of attenuated live vaccines within 14 days prior to booster vaccination; receipt of inactivated or subunit vaccines within 7 days prior to booster vaccination; acute diseases or acute exacerbation of chronic diseases within 7 days prior to booster vaccination; axillary temperature >37.0°c prior to booster vaccination; according to the investigator's judgment, the subject has any other factors that are not suitable for participating in the clinical trial