1. chest x - ray is clinically significant abnormal as determined by the investigators 2. the vital signs or examinations are clinically significant abnormal as determined by the investigators prior to randomization 3. a history of severe allergy (including drugs, vaccines, and foods) or to any component of the experimental vaccine, e.g., allergic shock, allergic laryngeal edema, anaphylactoid purpura, dyspnea, and angioedema, etc. 4. subjects have been diagnosed with a serious disease, congenital malformation or chronic disease (including but not limited to: respiratory disease or chronic bronchitis such as asthma, serious cardiovascular disease, kidney disease, autoimmune disease, thrombocytopenic purpura, thalassemia, malignant tumor, hereditary allergic constitution, etc.) that may interfere with the conduct or completion of the study 5. diagnosed with diseases may affect immune system function, congenital or acquired immune deficiency or suppression (e.g., tuberculosis, human immunodeficiency virus (hiv)), hepatitis b, hepatitis c, syphilis infection, uncontrollable autoimmune disease, no spleen or spleen dysfunction 6. lymph node - related diseases (such as lymphadenitis, lymph node adhesion, lymph node tuberculosis, tumor metastasis, etc.) or skin scars and fistulas at the lymph node site, or lymphadenopathy, tenderness, skin redness and swelling at the lymph node site within 7 days prior to injection 7. history or family history of convulsions, epilepsy, encephalopathy, psychiatry, or history of narcolepsy 8. within 3 days prior to injection, an acute illness or attack of a chronic disease, or the use of antipyretic analgesic or anti - allergic drugs 9. subjects have contraindications to intramuscular injection, such as having been diagnosed with thrombocytopenia, any blood clotting disorder or receiving anticoagulant therapy 10. long-term use of immunopotentiator or immunosuppressant therapy within 6 months prior to the first dose injection (continuous orally or by injection for more than 14 days). 11. use of any blood or blood - related products (e.g., blood transfusion, use of human albumin, human immunoglobulin, etc.) within 6 months prior to the first dose injection 12. any blood lost \> 400 ml within 28 days prior to the screening visit (e.g., donate blood or component blood, or injured), or plan to donate blood or component blood between the screening visit and 28 days after the last dose injection 13. previously received any sars-cov-2 vaccine or plan to receive other sars-cov-2 vaccines 14. other vaccines have been administered within 4 weeks prior to the first dose injection or other injection schedule (except for emergency injections such as rabies vaccine and tetanus vaccine) between the screening period and 28 days after the injection 15. any abnormal or permanent body art (such as tattoos) at the site of the injection, which the researchers think to interfere with observing local reactions at the site of the injection 16. female subjects planning to become pregnant or male subjects' partners planning to become pregnant from screening period to 12 months after whole schedule injection 17. participating in or planning to participate in other clinical trials (drugs or vaccines) within 3 months prior to participating in this study 18. other circumstances considered by the investigator as inappropriate to participate in the study

1. chest x - ray is clinically significant abnormal as determined by the investigators 2. the vital signs or examinations are clinically significant abnormal as determined by the investigators prior to randomization 3. a history of severe allergy (including drugs, vaccines, and foods) or to any component of the experimental vaccine, e.g., allergic shock, allergic laryngeal edema, anaphylactoid purpura, dyspnea, and angioedema, etc. 4. subjects have been diagnosed with a serious disease, congenital malformation or chronic disease (including but not limited to: respiratory disease or chronic bronchitis such as asthma, serious cardiovascular disease, kidney disease, autoimmune disease, thrombocytopenic purpura, thalassemia, malignant tumor, hereditary allergic constitution, etc.) that may interfere with the conduct or completion of the study 5. diagnosed with diseases may affect immune system function, congenital or acquired immune deficiency or suppression (e.g., tuberculosis, human immunodeficiency virus (hiv)), hepatitis b, hepatitis c, syphilis infection, uncontrollable autoimmune disease, no spleen or spleen dysfunction 6. lymph node - related diseases (such as lymphadenitis, lymph node adhesion, lymph node tuberculosis, tumor metastasis, etc.) or skin scars and fistulas at the lymph node site, or lymphadenopathy, tenderness, skin redness and swelling at the lymph node site within 7 days prior to injection 7. history or family history of convulsions, epilepsy, encephalopathy, psychiatry, or history of narcolepsy 8. within 3 days prior to injection, an acute illness or attack of a chronic disease, or the use of antipyretic analgesic or anti - allergic drugs 9. subjects have contraindications to intramuscular injection, such as having been diagnosed with thrombocytopenia, any blood clotting disorder or receiving anticoagulant therapy 10. long-term use of immunopotentiator or immunosuppressant therapy within 6 months prior to the first dose injection (continuous orally or by injection for more than 14 days). 11. use of any blood or blood - related products (e.g., blood transfusion, use of human albumin, human immunoglobulin, etc.) within 6 months prior to the first dose injection 12. any blood lost \> 400 ml within 28 days prior to the screening visit (e.g., donate blood or component blood, or injured), or plan to donate blood or component blood between the screening visit and 28 days after the last dose injection 13. previously received any sars-cov-2 vaccine or plan to receive other sars-cov-2 vaccines 14. other vaccines have been administered within 4 weeks prior to the first dose injection or other injection schedule (except for emergency injections such as rabies vaccine and tetanus vaccine) between the screening period and 28 days after the injection 15. any abnormal or permanent body art (such as tattoos) at the site of the injection, which the researchers think to interfere with observing local reactions at the site of the injection 16. female subjects planning to become pregnant or male subjects' partners planning to become pregnant from screening period to 12 months after whole schedule injection 17. participating in or planning to participate in other clinical trials (drugs or vaccines) within 3 months prior to participating in this study 18. other circumstances considered by the investigator as inappropriate to participate in the study

chest x - ray is clinically significant abnormal as determined by the investigators the vital signs or examinations are clinically significant abnormal as determined by the investigators prior to randomization a history of severe allergy (including drugs, vaccines, and foods) or to any component of the experimental vaccine, e.g., allergic shock, allergic laryngeal edema, anaphylactoid purpura, dyspnea, and angioedema, etc. subjects have been diagnosed with a serious disease, congenital malformation or chronic disease (including but not limited to: respiratory disease or chronic bronchitis such as asthma, serious cardiovascular disease, kidney disease, autoimmune disease, thrombocytopenic purpura, thalassemia, malignant tumor, hereditary allergic constitution, etc.) that may interfere with the conduct or completion of the study diagnosed with diseases may affect immune system function, congenital or acquired immune deficiency or suppression (e.g., tuberculosis, human immunodeficiency virus (hiv)), hepatitis b, hepatitis c, syphilis infection, uncontrollable autoimmune disease, no spleen or spleen dysfunction lymph node - related diseases (such as lymphadenitis, lymph node adhesion, lymph node tuberculosis, tumor metastasis, etc.) or skin scars and fistulas at the lymph node site, or lymphadenopathy, tenderness, skin redness and swelling at the lymph node site within 7 days prior to injection history or family history of convulsions, epilepsy, encephalopathy, psychiatry, or history of narcolepsy within 3 days prior to injection, an acute illness or attack of a chronic disease, or the use of antipyretic analgesic or anti - allergic drugs subjects have contraindications to intramuscular injection, such as having been diagnosed with thrombocytopenia, any blood clotting disorder or receiving anticoagulant therapy long-term use of immunopotentiator or immunosuppressant therapy within 6 months prior to the first dose injection (continuous orally or by injection for more than 14 days). use of any blood or blood - related products (e.g., blood transfusion, use of human albumin, human immunoglobulin, etc.) within 6 months prior to the first dose injection any blood lost > 400 ml within 28 days prior to the screening visit (e.g., donate blood or component blood, or injured), or plan to donate blood or component blood between the screening visit and 28 days after the last dose injection previously received any sars-cov-2 vaccine or plan to receive other sars-cov-2 vaccines other vaccines have been administered within 4 weeks prior to the first dose injection or other injection schedule (except for emergency injections such as rabies vaccine and tetanus vaccine) between the screening period and 28 days after the injection any abnormal or permanent body art (such as tattoos) at the site of the injection, which the researchers think to interfere with observing local reactions at the site of the injection female subjects planning to become pregnant or male subjects' partners planning to become pregnant from screening period to 12 months after whole schedule injection participating in or planning to participate in other clinical trials (drugs or vaccines) within 3 months prior to participating in this study other circumstances considered by the investigator as inappropriate to participate in the study

chest x - ray is clinically significant abnormal as determined by the investigators the vital signs or examinations are clinically significant abnormal as determined by the investigators prior to randomization a history of severe allergy (including drugs, vaccines, and foods) or to any component of the experimental vaccine, e.g., allergic shock, allergic laryngeal edema, anaphylactoid purpura, dyspnea, and angioedema, etc. subjects have been diagnosed with a serious disease, congenital malformation or chronic disease (including but not limited to: respiratory disease or chronic bronchitis such as asthma, serious cardiovascular disease, kidney disease, autoimmune disease, thrombocytopenic purpura, thalassemia, malignant tumor, hereditary allergic constitution, etc.) that may interfere with the conduct or completion of the study diagnosed with diseases may affect immune system function, congenital or acquired immune deficiency or suppression (e.g., tuberculosis, human immunodeficiency virus (hiv)), hepatitis b, hepatitis c, syphilis infection, uncontrollable autoimmune disease, no spleen or spleen dysfunction lymph node - related diseases (such as lymphadenitis, lymph node adhesion, lymph node tuberculosis, tumor metastasis, etc.) or skin scars and fistulas at the lymph node site, or lymphadenopathy, tenderness, skin redness and swelling at the lymph node site within 7 days prior to injection history or family history of convulsions, epilepsy, encephalopathy, psychiatry, or history of narcolepsy within 3 days prior to injection, an acute illness or attack of a chronic disease, or the use of antipyretic analgesic or anti - allergic drugs subjects have contraindications to intramuscular injection, such as having been diagnosed with thrombocytopenia, any blood clotting disorder or receiving anticoagulant therapy long-term use of immunopotentiator or immunosuppressant therapy within 6 months prior to the first dose injection (continuous orally or by injection for more than 14 days). use of any blood or blood - related products (e.g., blood transfusion, use of human albumin, human immunoglobulin, etc.) within 6 months prior to the first dose injection any blood lost > 400 ml within 28 days prior to the screening visit (e.g., donate blood or component blood, or injured), or plan to donate blood or component blood between the screening visit and 28 days after the last dose injection previously received any sars-cov-2 vaccine or plan to receive other sars-cov-2 vaccines other vaccines have been administered within 4 weeks prior to the first dose injection or other injection schedule (except for emergency injections such as rabies vaccine and tetanus vaccine) between the screening period and 28 days after the injection any abnormal or permanent body art (such as tattoos) at the site of the injection, which the researchers think to interfere with observing local reactions at the site of the injection female subjects planning to become pregnant or male subjects' partners planning to become pregnant from screening period to 12 months after whole schedule injection participating in or planning to participate in other clinical trials (drugs or vaccines) within 3 months prior to participating in this study other circumstances considered by the investigator as inappropriate to participate in the study