* presence of fever within 72 h before vaccination (axillary temperature ≥ 37.3℃), or active tuberculosis, or in the acute phase of other diseases; * a history of severe acute respiratory syndrome (sars), middle east respiratory syndrome (mers), or other coronavirus infections or illness or relevant * a history of allergic reactions to any vaccine or drug, such as allergy, urticaria, severe skin eczema, dyspnea, laryngeal edema, and angioneurotic edema; * a medical or family history of seizure, epilepsy, encephalopathy and psychosis; * immunocompromised patients suffering or suffered from immunodeficiency diseases, important organ diseases, or immune diseases, etc.; * long-term use of immunosuppressive or immunomodulatory drugs for 14 or more days within 6 months prior to study enrollment, or planned use of immunosuppressive or immunomodulatory drugs within 2 years after study enrollment. the use of inhaled and topical corticosteroid is permitted; * for phase i participants only: previously or currently suffering from clinically significant cardiovascular diseases (except for the hypertension that can be controlled with drugs), or clinically significant disorders related to respiratory system, liver and kidney (except for light fatty liver), gastrointestinal system (except for chronic gastritis), endocrine system, blood and lymphatic system, metabolic and skeletal systems, or malignancies (except for skin basal cell carcinoma and carcinoma in-situ of cervix), that may affect the study assessment, or cause risks during the study vaccination, or interfere with the data interpretation as determined by the investigator; for phase ii participants only: presence of severe or uncontrollable cardiovascular diseases, or severe or uncontrollable disorders related to endocrine system, blood and lymphatic system, liver and kidney, respiratory system, metabolic and skeletal systems, or malignancies (except for skin basal cell carcinoma and carcinoma in-situ of cervix); * contraindications for intramuscular injection or intravenous blood sampling, including thrombocytopenia and other blood coagulation disorders; * participants who received any immunoglobulin or blood products in the previous 3 months, or plan to receive similar products during the study; * participants who received other intervention investigational drugs within 1 month before the vaccination (except for the participants in the saline control group participating in the clinical study of covid-19 vaccine); * participants vaccinated with influenza vaccine within 14 days, or with other type of vaccines within 28 days before the vaccination; * those who donated blood or had blood loss (≥450 ml) within 3 months before the first dose vaccination or plan to donate blood during the study period; * those who are pregnant or breast-feeding; * those who plan to donate ovum or sperms during the study period; * those who cannot follow the study procedures, or cannot cooperate to complete the study due to planned relocation or long-term outing; * those unsuitable for participating in the clinical study as determined by the investigator because of other abnormalities that are likely to confuse the study results, or non-conformance with the maximal benefits of the participants; * for phase i participants only: those who are tested positive for hepatitis b virus (hbv), hepatitis c virus (hcv), syphilis or hiv in terms of etiology or serology; for phase ii participants only: those who are tested positive for hiv in terms of etiology or serology.

* presence of fever within 72 h before vaccination (axillary temperature ≥ 37.3℃), or active tuberculosis, or in the acute phase of other diseases; * a history of severe acute respiratory syndrome (sars), middle east respiratory syndrome (mers), or other coronavirus infections or illness or relevant * a history of allergic reactions to any vaccine or drug, such as allergy, urticaria, severe skin eczema, dyspnea, laryngeal edema, and angioneurotic edema; * a medical or family history of seizure, epilepsy, encephalopathy and psychosis; * immunocompromised patients suffering or suffered from immunodeficiency diseases, important organ diseases, or immune diseases, etc.; * long-term use of immunosuppressive or immunomodulatory drugs for 14 or more days within 6 months prior to study enrollment, or planned use of immunosuppressive or immunomodulatory drugs within 2 years after study enrollment. the use of inhaled and topical corticosteroid is permitted; * for phase i participants only: previously or currently suffering from clinically significant cardiovascular diseases (except for the hypertension that can be controlled with drugs), or clinically significant disorders related to respiratory system, liver and kidney (except for light fatty liver), gastrointestinal system (except for chronic gastritis), endocrine system, blood and lymphatic system, metabolic and skeletal systems, or malignancies (except for skin basal cell carcinoma and carcinoma in-situ of cervix), that may affect the study assessment, or cause risks during the study vaccination, or interfere with the data interpretation as determined by the investigator; for phase ii participants only: presence of severe or uncontrollable cardiovascular diseases, or severe or uncontrollable disorders related to endocrine system, blood and lymphatic system, liver and kidney, respiratory system, metabolic and skeletal systems, or malignancies (except for skin basal cell carcinoma and carcinoma in-situ of cervix); * contraindications for intramuscular injection or intravenous blood sampling, including thrombocytopenia and other blood coagulation disorders; * participants who received any immunoglobulin or blood products in the previous 3 months, or plan to receive similar products during the study; * participants who received other intervention investigational drugs within 1 month before the vaccination (except for the participants in the saline control group participating in the clinical study of covid-19 vaccine); * participants vaccinated with influenza vaccine within 14 days, or with other type of vaccines within 28 days before the vaccination; * those who donated blood or had blood loss (≥450 ml) within 3 months before the first dose vaccination or plan to donate blood during the study period; * those who are pregnant or breast-feeding; * those who plan to donate ovum or sperms during the study period; * those who cannot follow the study procedures, or cannot cooperate to complete the study due to planned relocation or long-term outing; * those unsuitable for participating in the clinical study as determined by the investigator because of other abnormalities that are likely to confuse the study results, or non-conformance with the maximal benefits of the participants; * for phase i participants only: those who are tested positive for hepatitis b virus (hbv), hepatitis c virus (hcv), syphilis or hiv in terms of etiology or serology; for phase ii participants only: those who are tested positive for hiv in terms of etiology or serology.

presence of fever within 72 h before vaccination (axillary temperature ≥ 37.3℃), or active tuberculosis, or in the acute phase of other diseases; a history of severe acute respiratory syndrome (sars), middle east respiratory syndrome (mers), or other coronavirus infections or illness or relevant a history of allergic reactions to any vaccine or drug, such as allergy, urticaria, severe skin eczema, dyspnea, laryngeal edema, and angioneurotic edema; a medical or family history of seizure, epilepsy, encephalopathy and psychosis; immunocompromised patients suffering or suffered from immunodeficiency diseases, important organ diseases, or immune diseases, etc.; long-term use of immunosuppressive or immunomodulatory drugs for 14 or more days within 6 months prior to study enrollment, or planned use of immunosuppressive or immunomodulatory drugs within 2 years after study enrollment. the use of inhaled and topical corticosteroid is permitted; for phase i participants only: previously or currently suffering from clinically significant cardiovascular diseases (except for the hypertension that can be controlled with drugs), or clinically significant disorders related to respiratory system, liver and kidney (except for light fatty liver), gastrointestinal system (except for chronic gastritis), endocrine system, blood and lymphatic system, metabolic and skeletal systems, or malignancies (except for skin basal cell carcinoma and carcinoma in-situ of cervix), that may affect the study assessment, or cause risks during the study vaccination, or interfere with the data interpretation as determined by the investigator; for phase ii participants only: presence of severe or uncontrollable cardiovascular diseases, or severe or uncontrollable disorders related to endocrine system, blood and lymphatic system, liver and kidney, respiratory system, metabolic and skeletal systems, or malignancies (except for skin basal cell carcinoma and carcinoma in-situ of cervix); contraindications for intramuscular injection or intravenous blood sampling, including thrombocytopenia and other blood coagulation disorders; participants who received any immunoglobulin or blood products in the previous 3 months, or plan to receive similar products during the study; participants who received other intervention investigational drugs within 1 month before the vaccination (except for the participants in the saline control group participating in the clinical study of covid-19 vaccine); participants vaccinated with influenza vaccine within 14 days, or with other type of vaccines within 28 days before the vaccination; those who donated blood or had blood loss (≥450 ml) within 3 months before the first dose vaccination or plan to donate blood during the study period; those who are pregnant or breast-feeding; those who plan to donate ovum or sperms during the study period; those who cannot follow the study procedures, or cannot cooperate to complete the study due to planned relocation or long-term outing; those unsuitable for participating in the clinical study as determined by the investigator because of other abnormalities that are likely to confuse the study results, or non-conformance with the maximal benefits of the participants; for phase i participants only: those who are tested positive for hepatitis b virus (hbv), hepatitis c virus (hcv), syphilis or hiv in terms of etiology or serology; for phase ii participants only: those who are tested positive for hiv in terms of etiology or serology.

presence of fever within 72 h before vaccination (axillary temperature ≥ 37.3℃), or active tuberculosis, or in the acute phase of other diseases; a history of severe acute respiratory syndrome (sars), middle east respiratory syndrome (mers), or other coronavirus infections or illness or relevant a history of allergic reactions to any vaccine or drug, such as allergy, urticaria, severe skin eczema, dyspnea, laryngeal edema, and angioneurotic edema; a medical or family history of seizure, epilepsy, encephalopathy and psychosis; immunocompromised patients suffering or suffered from immunodeficiency diseases, important organ diseases, or immune diseases, etc.; long-term use of immunosuppressive or immunomodulatory drugs for 14 or more days within 6 months prior to study enrollment, or planned use of immunosuppressive or immunomodulatory drugs within 2 years after study enrollment. the use of inhaled and topical corticosteroid is permitted; for phase i participants only: previously or currently suffering from clinically significant cardiovascular diseases (except for the hypertension that can be controlled with drugs), or clinically significant disorders related to respiratory system, liver and kidney (except for light fatty liver), gastrointestinal system (except for chronic gastritis), endocrine system, blood and lymphatic system, metabolic and skeletal systems, or malignancies (except for skin basal cell carcinoma and carcinoma in-situ of cervix), that may affect the study assessment, or cause risks during the study vaccination, or interfere with the data interpretation as determined by the investigator; for phase ii participants only: presence of severe or uncontrollable cardiovascular diseases, or severe or uncontrollable disorders related to endocrine system, blood and lymphatic system, liver and kidney, respiratory system, metabolic and skeletal systems, or malignancies (except for skin basal cell carcinoma and carcinoma in-situ of cervix); contraindications for intramuscular injection or intravenous blood sampling, including thrombocytopenia and other blood coagulation disorders; participants who received any immunoglobulin or blood products in the previous 3 months, or plan to receive similar products during the study; participants who received other intervention investigational drugs within 1 month before the vaccination (except for the participants in the saline control group participating in the clinical study of covid-19 vaccine); participants vaccinated with influenza vaccine within 14 days, or with other type of vaccines within 28 days before the vaccination; those who donated blood or had blood loss (≥450 ml) within 3 months before the first dose vaccination or plan to donate blood during the study period; those who are pregnant or breast-feeding; those who plan to donate ovum or sperms during the study period; those who cannot follow the study procedures, or cannot cooperate to complete the study due to planned relocation or long-term outing; those unsuitable for participating in the clinical study as determined by the investigator because of other abnormalities that are likely to confuse the study results, or non-conformance with the maximal benefits of the participants; for phase i participants only: those who are tested positive for hepatitis b virus (hbv), hepatitis c virus (hcv), syphilis or hiv in terms of etiology or serology; for phase ii participants only: those who are tested positive for hiv in terms of etiology or serology.