1) Be at least 18 years old at the time of entry, 2) Able to comply with the requirements of the clinical research plan to complete all trial procedures and sign the informed consent form, 3) For female subjects: infertility (surgical sterilization or at least one year after menopause) or willing to use appropriate contraceptive measures from 30 days before vaccination to 3 months after vaccination, including abstinence or effective contraception measures (such as intrauterine or implantable contraceptive devices, oral contraceptives, uterine diaphragm or condoms combined with contraceptive gel), 4) For subjects in the sequential subgroup: complete two doses of inactivated COVID-19 vaccine 28 to 60 days before enrollment, 5) Healthy subjects with past illnesses: within 3 months before enrollment, the condition was stable without deterioration, hospitalization or major changes in treatment, such as hypertension (controlled at systolic blood pressure <140mmHg, diastolic blood pressure <90mmHg, diabetes, asthma, thyroid disease, etc.

1) Be at least 18 years old at the time of entry, 2) Able to comply with the requirements of the clinical research plan to complete all trial procedures and sign the informed consent form, 3) For female subjects: infertility (surgical sterilization or at least one year after menopause) or willing to use appropriate contraceptive measures from 30 days before vaccination to 3 months after vaccination, including abstinence or effective contraception measures (such as intrauterine or implantable contraceptive devices, oral contraceptives, uterine diaphragm or condoms combined with contraceptive gel), 4) For subjects in the sequential subgroup: complete two doses of inactivated COVID-19 vaccine 28 to 60 days before enrollment, 5) Healthy subjects with past illnesses: within 3 months before enrollment, the condition was stable without deterioration, hospitalization or major changes in treatment, such as hypertension (controlled at systolic blood pressure <140mmHg, diastolic blood pressure <90mmHg, diabetes, asthma, thyroid disease, etc.