history of sars-cov-2 infection(laboratory confirmed); close contact with a confirmed covid-19 (nucleic acid test or antigen test positive patients)within 14 days prior to randomization; received other covid-19 vaccine in the past except for two or three doses of prototype vaccine; allergy to vaccines or vaccine/placebo ingredients, and serious adverse reactions to vaccines, such as urticaria, dyspnea, angioneuroedema; autoimmune disease and/or blood disease history (including but not limited to systemic lupus erythematosus, thyroidectomy, autoimmune thyroid disease, any form of malignancy, absence of spleen, functional absence of spleen, or splenectomy for any condition),patients with well-controlled type 1 diabetes can be enrolled; serious chronic diseases, such as serious cardiovascular diseases, hypertension, diabetes, liver and kidney diseases, malignant tumors, etc; severe neurological disease (epilepsy, convulsions or convulsions) or mental illness; diagnosed abnormal blood coagulation function (eg, lack of blood coagulation factors, blood coagulopathy, abnormal platelets) or obvious bruising or blood coagulation; immunosuppressive therapy, cytotoxic therapy, inhaled corticosteroids (excluding allergic rhinitis corticosteroid spray therapy, acute noncomplicated dermatitis superficial corticosteroid therapy) in the past 6 months; long-term history of alcohol or drug abuse; received blood products within 3 months prior to receiving the investigational vaccine, or planning to receive the above treatments during the study period; receipt of other investigational drugs in the past 30 days; receipt of attenuated live vaccines in the past 14 days; receipt of inactivated or subunit vaccines in the past 7 days; onset of various acute or chronic diseases within 7 days prior to the study; in case of fever on the day of planned trial vaccine inoculation,axillary temperature >37.0°c; women who are breastfeeding, pregnant, or planning to become pregnant during the study period (based on subjects' self-reported and urine pregnancy test results); participating in or planning to participate in clinical trials of other vaccines or drugs; 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(laboratory confirmed); close contact with a confirmed covid-19 (nucleic acid test or antigen test positive patients)within 14 days prior to randomization; received other covid-19 vaccine in the past except for two or three doses of prototype vaccine; allergy to vaccines or vaccine/placebo ingredients, and serious adverse reactions to vaccines, such as urticaria, dyspnea, angioneuroedema; autoimmune disease and/or blood disease history (including but not limited to systemic lupus erythematosus, thyroidectomy, autoimmune thyroid disease, any form of malignancy, absence of spleen, functional absence of spleen, or splenectomy for any condition),patients with well-controlled type 1 diabetes can be enrolled; serious chronic diseases, such as serious cardiovascular diseases, hypertension, diabetes, liver and kidney diseases, malignant tumors, etc; severe neurological disease (epilepsy, convulsions or convulsions) or mental illness; diagnosed abnormal blood coagulation function (eg, lack of blood coagulation factors, blood coagulopathy, abnormal platelets) or obvious bruising or blood coagulation; immunosuppressive therapy, cytotoxic therapy, inhaled corticosteroids (excluding allergic rhinitis corticosteroid spray therapy, acute noncomplicated dermatitis superficial corticosteroid therapy) in the past 6 months; long-term history of alcohol or drug abuse; received blood products within 3 months prior to receiving the investigational vaccine, or planning to receive the above treatments during the study period; receipt of other investigational drugs in the past 30 days; receipt of attenuated live vaccines in the past 14 days; receipt of inactivated or subunit vaccines in the past 7 days; onset of various acute or chronic diseases within 7 days prior to the study; in case of fever on the day of planned trial vaccine inoculation,axillary temperature >37.0°c; women who are breastfeeding, pregnant, or planning to become pregnant during the study period (based on subjects' self-reported and urine pregnancy test results); participating in or planning to participate in clinical trials of other vaccines or drugs; 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(laboratory confirmed); close contact with a confirmed covid-19 (nucleic acid test or antigen test positive patients)within 14 days prior to randomization; received other covid-19 vaccine in the past except for two or three doses of prototype vaccine; allergy to vaccines or vaccine/placebo ingredients, and serious adverse reactions to vaccines, such as urticaria, dyspnea, angioneuroedema; autoimmune disease and/or blood history (including but not limited to systemic lupus erythematosus, thyroidectomy, autoimmune thyroid disease, any form of malignancy, absence of spleen, functional absence of spleen, or splenectomy for any condition),patients with well-controlled type 1 diabetes can be enrolled; serious chronic diseases, such as serious cardiovascular diseases, hypertension, diabetes, liver and kidney diseases, malignant tumors, etc; severe neurological disease (epilepsy, convulsions or convulsions) or mental illness; diagnosed abnormal blood coagulation function (eg, lack of blood coagulation factors, blood coagulopathy, abnormal platelets) or obvious bruising or blood coagulation; immunosuppressive therapy, cytotoxic therapy, inhaled corticosteroids (excluding allergic rhinitis corticosteroid spray therapy, acute noncomplicated dermatitis superficial corticosteroid therapy) in the past 6 months; history of alcohol or drug abuse; receipt of blood products within in the past 3 months receipt of other investigational drugs in the past 30 days receipt of attenuated live vaccines in the past 14 days; receipt of inactivated or subunit vaccines in the past 7 days; onset of various acute or chronic diseases within 7 days prior to the study; in case of fever on the day of planned trial vaccine inoculation,axillary temperature >37.0°c; women who are breastfeeding, pregnant, or planning to become pregnant during the study period (based on subjects' self-reported and urine pregnancy test results); participating in or planning to participate in clinical trials of other vaccines or drugs; 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(laboratory confirmed); close contact with a confirmed covid-19 (nucleic acid test or antigen test positive patients)within 14 days prior to randomization; received other covid-19 vaccine in the past except for two or three doses of prototype vaccine; allergy to vaccines or vaccine/placebo ingredients, and serious adverse reactions to vaccines, such as urticaria, dyspnea, angioneuroedema; autoimmune disease and/or blood history (including but not limited to systemic lupus erythematosus, thyroidectomy, autoimmune thyroid disease, any form of malignancy, absence of spleen, functional absence of spleen, or splenectomy for any condition),patients with well-controlled type 1 diabetes can be enrolled; serious chronic diseases, such as serious cardiovascular diseases, hypertension, diabetes, liver and kidney diseases, malignant tumors, etc; severe neurological disease (epilepsy, convulsions or convulsions) or mental illness; diagnosed abnormal blood coagulation function (eg, lack of blood coagulation factors, blood coagulopathy, abnormal platelets) or obvious bruising or blood coagulation; immunosuppressive therapy, cytotoxic therapy, inhaled corticosteroids (excluding allergic rhinitis corticosteroid spray therapy, acute noncomplicated dermatitis superficial corticosteroid therapy) in the past 6 months; history of alcohol or drug abuse; receipt of blood products within in the past 3 months receipt of other investigational drugs in the past 30 days receipt of attenuated live vaccines in the past 14 days; receipt of inactivated or subunit vaccines in the past 7 days; onset of various acute or chronic diseases within 7 days prior to the study; in case of fever on the day of planned trial vaccine inoculation,axillary temperature >37.0°c; women who are breastfeeding, pregnant, or planning to become pregnant during the study period (based on subjects' self-reported and urine pregnancy test results); participating in or planning to participate in clinical trials of other vaccines or drugs; according to the investigator's judgment, the subject has any other factors that are not suitable for participating in the clinical trial.