* positive sars-cov-2 antibodies (igg or igm) screening results. * positive sars-cov-2 antigen screening results. * history of covid-19 vaccination. * previously diagnosed with covid-19 infection. * history of hiv infection. * history or family history of convulsion, epilepsy, encephalopathy and psychosis. * allergy to any component of the candidate vaccine, severe allergy to vaccine in the past, and history of allergy. * women with positive urine pregnancy test results, pregnant, lactating women, or women who have a pregnancy plan during the study. * patients with acute febrile diseases and infectious diseases. * patients with a history of sars. * serious cardiovascular diseases, such as arrhythmia, conduction block, myocardial infarction, severe hypertension that cannot be controlled by drugs, etc. * serious chronic diseases or progressive stage of a disease that cannot be steadily controlled, such as asthma, diabetes mellitus, thyroid disease, etc. * congenital or acquired angioedema/angioneurotic edema. * urticaria 1 year before receiving the candidate vaccine. * asplenia or functional asplenia. * thrombocytopenia or other coagulation disorders (which may contraindicate intramuscular injection). * fear of needles. * any immunosuppressant, antiallergic therapy, cytotoxic medicine, or inhaled corticosteroids (except corticosteroid spray for treatment of allergic rhinitis or corticosteroid treatment on surface for acute non-complicated dermatitis) in the past 6 months. * blood products within 4 months prior to receiving the candidate vaccine. * any other investigational medicine(s) within 1 month prior to the candidate vaccine. * any live attenuated vaccine within 1 month prior to the candidate vaccine. * any subunit vaccine or inactivated vaccine within 14 days prior to the candidate vaccine. * receiving antituberculosis treatment. * medical, psychological, social or other factors, which in the discretion of the investigators fail to meet the requirements in the trial protocol or affect the subjects to sign the icfs. exclusion criteria for the second/third dose: in this trial, the second/third vaccination may be stopped in some cases. they include systemic allergic reaction, severe hypersensitivity, or intolerable grade 3 or above ars after the previous dose of vaccine. if these reactions occur, the subjects should not continue to receive the second/third vaccination.

* positive sars-cov-2 antibodies (igg or igm) screening results. * positive sars-cov-2 antigen screening results. * history of covid-19 vaccination. * previously diagnosed with covid-19 infection. * history of hiv infection. * history or family history of convulsion, epilepsy, encephalopathy and psychosis. * allergy to any component of the candidate vaccine, severe allergy to vaccine in the past, and history of allergy. * women with positive urine pregnancy test results, pregnant, lactating women, or women who have a pregnancy plan during the study. * patients with acute febrile diseases and infectious diseases. * patients with a history of sars. * serious cardiovascular diseases, such as arrhythmia, conduction block, myocardial infarction, severe hypertension that cannot be controlled by drugs, etc. * serious chronic diseases or progressive stage of a disease that cannot be steadily controlled, such as asthma, diabetes mellitus, thyroid disease, etc. * congenital or acquired angioedema/angioneurotic edema. * urticaria 1 year before receiving the candidate vaccine. * asplenia or functional asplenia. * thrombocytopenia or other coagulation disorders (which may contraindicate intramuscular injection). * fear of needles. * any immunosuppressant, antiallergic therapy, cytotoxic medicine, or inhaled corticosteroids (except corticosteroid spray for treatment of allergic rhinitis or corticosteroid treatment on surface for acute non-complicated dermatitis) in the past 6 months. * blood products within 4 months prior to receiving the candidate vaccine. * any other investigational medicine(s) within 1 month prior to the candidate vaccine. * any live attenuated vaccine within 1 month prior to the candidate vaccine. * any subunit vaccine or inactivated vaccine within 14 days prior to the candidate vaccine. * receiving antituberculosis treatment. * medical, psychological, social or other factors, which in the discretion of the investigators fail to meet the requirements in the trial protocol or affect the subjects to sign the icfs. exclusion criteria for the second/third dose: in this trial, the second/third vaccination may be stopped in some cases. they include systemic allergic reaction, severe hypersensitivity, or intolerable grade 3 or above ars after the previous dose of vaccine. if these reactions occur, the subjects should not continue to receive the second/third vaccination.

positive sars-cov-2 antibodies (igg or igm) screening results. positive sars-cov-2 antigen screening results. history of covid-19 vaccination. previously diagnosed with covid-19 infection. history of hiv infection. history or family history of convulsion, epilepsy, encephalopathy and psychosis. allergy to any component of the candidate vaccine, severe allergy to vaccine in the past, and history of allergy. women with positive urine pregnancy test results, pregnant, lactating women, or women who have a pregnancy plan during the study. patients with acute febrile diseases and infectious diseases. patients with a history of sars. serious cardiovascular diseases, such as arrhythmia, conduction block, myocardial infarction, severe hypertension that cannot be controlled by drugs, etc. serious chronic diseases or progressive stage of a disease that cannot be steadily controlled, such as asthma, diabetes mellitus, thyroid disease, etc. congenital or acquired angioedema/angioneurotic edema. urticaria 1 year before receiving the candidate vaccine. asplenia or functional asplenia. thrombocytopenia or other coagulation disorders (which may contraindicate intramuscular injection). fear of needles. any immunosuppressant, antiallergic therapy, cytotoxic medicine, or inhaled corticosteroids (except corticosteroid spray for treatment of allergic rhinitis or corticosteroid treatment on surface for acute non-complicated dermatitis) in the past 6 months. blood products within 4 months prior to receiving the candidate vaccine. any other investigational medicine(s) within 1 month prior to the candidate vaccine. any live attenuated vaccine within 1 month prior to the candidate vaccine. any subunit vaccine or inactivated vaccine within 14 days prior to the candidate vaccine. receiving antituberculosis treatment. medical, psychological, social or other factors, which in the discretion of the investigators fail to meet the requirements in the trial protocol or affect the subjects to sign the icfs. exclusion criteria for the second/third dose: in this trial, the second/third vaccination may be stopped in some cases. they include systemic allergic reaction, severe hypersensitivity, or intolerable grade 3 or above ars after the previous dose of vaccine. if these reactions occur, the subjects should not continue to receive the second/third vaccination.

positive sars-cov-2 antibodies (igg or igm) screening results. positive sars-cov-2 antigen screening results. history of covid-19 vaccination. previously diagnosed with covid-19 infection. history of hiv infection. history or family history of convulsion, epilepsy, encephalopathy and psychosis. allergy to any component of the candidate vaccine, severe allergy to vaccine in the past, and history of allergy. women with positive urine pregnancy test results, pregnant, lactating women, or women who have a pregnancy plan during the study. patients with acute febrile diseases and infectious diseases. patients with a history of sars. serious cardiovascular diseases, such as arrhythmia, conduction block, myocardial infarction, severe hypertension that cannot be controlled by drugs, etc. serious chronic diseases or progressive stage of a disease that cannot be steadily controlled, such as asthma, diabetes mellitus, thyroid disease, etc. congenital or acquired angioedema/angioneurotic edema. urticaria 1 year before receiving the candidate vaccine. asplenia or functional asplenia. thrombocytopenia or other coagulation disorders (which may contraindicate intramuscular injection). fear of needles. any immunosuppressant, antiallergic therapy, cytotoxic medicine, or inhaled corticosteroids (except corticosteroid spray for treatment of allergic rhinitis or corticosteroid treatment on surface for acute non-complicated dermatitis) in the past 6 months. blood products within 4 months prior to receiving the candidate vaccine. any other investigational medicine(s) within 1 month prior to the candidate vaccine. any live attenuated vaccine within 1 month prior to the candidate vaccine. any subunit vaccine or inactivated vaccine within 14 days prior to the candidate vaccine. receiving antituberculosis treatment. medical, psychological, social or other factors, which in the discretion of the investigators fail to meet the requirements in the trial protocol or affect the subjects to sign the icfs. exclusion criteria for the second/third dose: in this trial, the second/third vaccination may be stopped in some cases. they include systemic allergic reaction, severe hypersensitivity, or intolerable grade 3 or above ars after the previous dose of vaccine. if these reactions occur, the subjects should not continue to receive the second/third vaccination.