- history of sars-cov-2 infection. - the covid-19 antibody (igg and igm) screening was positive. - history of asthma, history of allergy to vaccines or vaccine components, or severe adverse reactions to vaccines, such as urticaria, dyspnea, and angioedema. - congenital malformations or developmental disorders, genetic defects, severe malnutrition, etc. - autoimmune diseases or immunodeficiency/immunosuppression. - severe chronic diseases that cannot be controlled by drugs, severe cardiovascular diseases, diabetes, liver and kidney diseases, malignant tumors, etc. - severe neurological disease (epilepsy, convulsions or convulsions) or mental illness. - any condition caused by thyroid disease or history of thyroidectomy, hypersplenism, or splenectomy. - diagnosis of abnormal blood clotting function (for example, lack of clotting factors, coagulopathy, abnormal platelets) or obvious bruising or blood clotting. - in the past 6 months, received immunosuppressive therapy, cytotoxic therapy, inhaled corticosteroids (excluding corticosteroid spray therapy for allergic rhinitis, and superficial corticosteroid therapy for acute uncomplicated dermatitis). - laboratory test results with clinically significant abnormalities (severity level 2 and above) (applicable to phase i clinical trials only). - received blood products in the last 3 months. - receive other study drugs or vaccines within the past 30 days. - vaccination against live attenuated vaccines in the past 30 days. - inactivated vaccine or subunit vaccine in the past 14 days. - acute disease or acute exacerbation of chronic disease in the last 7 days. - axillary temperature> 37.0°c. - according to the judgment of the investigator, the subject has other factors that are not suitable for participating in the clinical trial. subsequent dose

- history of sars-cov-2 infection. - the covid-19 antibody (igg and igm) screening was positive. - history of asthma, history of allergy to vaccines or vaccine components, or severe adverse reactions to vaccines, such as urticaria, dyspnea, and angioedema. - congenital malformations or developmental disorders, genetic defects, severe malnutrition, etc. - autoimmune diseases or immunodeficiency/immunosuppression. - severe chronic diseases that cannot be controlled by drugs, severe cardiovascular diseases, diabetes, liver and kidney diseases, malignant tumors, etc. - severe neurological disease (epilepsy, convulsions or convulsions) or mental illness. - any condition caused by thyroid disease or history of thyroidectomy, hypersplenism, or splenectomy. - diagnosis of abnormal blood clotting function (for example, lack of clotting factors, coagulopathy, abnormal platelets) or obvious bruising or blood clotting. - in the past 6 months, received immunosuppressive therapy, cytotoxic therapy, inhaled corticosteroids (excluding corticosteroid spray therapy for allergic rhinitis, and superficial corticosteroid therapy for acute uncomplicated dermatitis). - laboratory test results with clinically significant abnormalities (severity level 2 and above) (applicable to phase i clinical trials only). - received blood products in the last 3 months. - receive other study drugs or vaccines within the past 30 days. - vaccination against live attenuated vaccines in the past 30 days. - inactivated vaccine or subunit vaccine in the past 14 days. - acute disease or acute exacerbation of chronic disease in the last 7 days. - axillary temperature> 37.0°c. - according to the judgment of the investigator, the subject has other factors that are not suitable for participating in the clinical trial. subsequent dose