1. For the elderly subjects, Baseline laboratory abnormalities with Grade >=3 (according to the grading criteria in appendix B) during screening visits, by physical examination and eligibility screening, 2. Have had any acute illness, as determined by the investigator, with or without fever, within 72 h prior to the prime vaccination. An acute illness which is nearly resolved with only minor residual symptoms remaining is allowable if, in the opinion of the investigator, the residual symptoms will not compromise their well-being if they participate as trial subjects in the trial, or that could prevent, limit, or confound the protocol-specified assessments, 3. Are breastfeeding on the day of Screening Visit or who plan to breastfeed during the trial, starting from Screening Visit and continuously until at least 90 days after the last immunization. Women or partners who plan to become pregnant within 1 year post the screening visit, 4. Have a known allergy, hypersensitivity, or intolerance to the planned vaccine for trial including any excipients, 5. Had a history of hypersensitivity or serious reactions to vaccination, 6. Received any vaccination within 4 weeks prior to Visit 1. 7. Disagree for do not receive other vaccine during the trial, starting from Screening Visit and continuously until 28 days after receiving the last immunization, except emergency vaccination (e.g. rabies vaccine, tetanus vaccine), 8. Had any medical condition (e.g., autoimmune disease) or any major surgery (e.g., requiring general anesthesia) within the past 5 years, which in the opinion of the investigator, could compromise their well-being if they participate as trial subjects in the trial, or that could prevent, limit, or confound the protocol-specified assessments. For the elderly subjects, Had any serious or life-threatening medical condition (e.g., autoimmune disease, cardiovascular disease) within the past 5 years, which in the opinion of the investigator, could compromise their well-being if they participate as trial subjects in the trial, or that could prevent, limit, or confound the protocol-specified assessments, 9. Have any surgery planned during the trial, starting from Screening Visit and continuously until at least 90 days after the last immunization, 10. Had any chronic use (more than 14 continuous days) of any systemic medications that affects immune function, including immunosuppressant or other immune-modifying drugs, within 6 months prior to Screening Visit unless in the opinion of the investigator, the medication would not prevent, limit, or confound the protocol-specified assessments or could compromise safety of subjects, 11. Had administration of any immunoglobulins and/or any blood products within the 3 months prior to Screening Visit. 12. Had administration of another investigational product including vaccines within 60 days or 5 half-lives (whichever is longer), prior to Screening Visit, 13. With known history of AIDS or HIV test positive, 14. History of HBV or HCV infection, through medical inquiry, 15. History of SARS, SARS-CoV-2 or MERS infection. Suspected SARS patients should be screened for SARS antibodies. 16. Previously participated in a clinical trial involving lipid nanoparticles, 17. Are subject to exclusion periods of other clinical trials or simultaneous participation in another clinical trial, 18. Have any affiliation with the study site (e.g., are close relative of the investigator or dependent person,

1. For the elderly subjects, Baseline laboratory abnormalities with Grade >=3 (according to the grading criteria in appendix B) during screening visits, by physical examination and eligibility screening, 2. Have had any acute illness, as determined by the investigator, with or without fever, within 72 h prior to the prime vaccination. An acute illness which is nearly resolved with only minor residual symptoms remaining is allowable if, in the opinion of the investigator, the residual symptoms will not compromise their well-being if they participate as trial subjects in the trial, or that could prevent, limit, or confound the protocol-specified assessments, 3. Are breastfeeding on the day of Screening Visit or who plan to breastfeed during the trial, starting from Screening Visit and continuously until at least 90 days after the last immunization. Women or partners who plan to become pregnant within 1 year post the screening visit, 4. Have a known allergy, hypersensitivity, or intolerance to the planned vaccine for trial including any excipients, 5. Had a history of hypersensitivity or serious reactions to vaccination, 6. Received any vaccination within 4 weeks prior to Visit 1. 7. Disagree for do not receive other vaccine during the trial, starting from Screening Visit and continuously until 28 days after receiving the last immunization, except emergency vaccination (e.g. rabies vaccine, tetanus vaccine), 8. Had any medical condition (e.g., autoimmune disease) or any major surgery (e.g., requiring general anesthesia) within the past 5 years, which in the opinion of the investigator, could compromise their well-being if they participate as trial subjects in the trial, or that could prevent, limit, or confound the protocol-specified assessments. For the elderly subjects, Had any serious or life-threatening medical condition (e.g., autoimmune disease, cardiovascular disease) within the past 5 years, which in the opinion of the investigator, could compromise their well-being if they participate as trial subjects in the trial, or that could prevent, limit, or confound the protocol-specified assessments, 9. Have any surgery planned during the trial, starting from Screening Visit and continuously until at least 90 days after the last immunization, 10. Had any chronic use (more than 14 continuous days) of any systemic medications that affects immune function, including immunosuppressant or other immune-modifying drugs, within 6 months prior to Screening Visit unless in the opinion of the investigator, the medication would not prevent, limit, or confound the protocol-specified assessments or could compromise safety of subjects, 11. Had administration of any immunoglobulins and/or any blood products within the 3 months prior to Screening Visit. 12. Had administration of another investigational product including vaccines within 60 days or 5 half-lives (whichever is longer), prior to Screening Visit, 13. With known history of AIDS or HIV test positive, 14. History of HBV or HCV infection, through medical inquiry, 15. History of SARS, SARS-CoV-2 or MERS infection. Suspected SARS patients should be screened for SARS antibodies. 16. Previously participated in a clinical trial involving lipid nanoparticles, 17. Are subject to exclusion periods of other clinical trials or simultaneous participation in another clinical trial, 18. Have any affiliation with the study site (e.g., are close relative of the investigator or dependent person,