inclusion criteria: age range: populations aged 18 years and above; judged by the investigator that the health condition is well after inquiry and physical examination; vaccinated with 2 doses of cnbg inactivated covid-19 vaccine according to the product insert; female subjects who are not nursing or pregnant at the time of enrolment (negative urine pregnancy test) and have no family planning within the first 6 months after enrolment. effective contraceptive measures have been taken within 2 weeks before inclusion. during the whole follow-up period of the study, be able and willing to complete the whole prescribed study plan; self has ability to understand the study procedures, the informed consent & voluntarily sign an informed consent form and is able to comply with the requirements of the clinical study protocol.

inclusion criteria: age range: populations aged 18 years and above; judged by the investigator that the health condition is well after inquiry and physical examination; vaccinated with 2 doses of cnbg inactivated covid-19 vaccine according to the product insert; female subjects who are not nursing or pregnant at the time of enrolment (negative urine pregnancy test) and have no family planning within the first 6 months after enrolment. effective contraceptive measures have been taken within 2 weeks before inclusion. during the whole follow-up period of the study, be able and willing to complete the whole prescribed study plan; self has ability to understand the study procedures, the informed consent & voluntarily sign an informed consent form and is able to comply with the requirements of the clinical study protocol.

inclusion criteria: - age range: populations aged 18 years and above; - judged by the investigator that the health condition is well after inquiry and physical examination; - vaccinated with 2 doses of cnbg inactivated covid-19 vaccine according to the product insert; - female subjects who are not nursing or pregnant at the time of enrolment (negative urine pregnancy test) and have no family planning within the first 3 months after enrolment. effective contraceptive measures have been taken within 2 weeks before inclusion. - during the whole follow-up period of the study, be able and willing to complete the whole prescribed study plan; self has ability to understand the study procedures, the informed consent & voluntarily sign an informed consent form and is able to comply with the requirements of the clinical study protocol.

inclusion criteria: - age range: populations aged 18 years and above; - judged by the investigator that the health condition is well after inquiry and physical examination; - vaccinated with 2 doses of cnbg inactivated covid-19 vaccine according to the product insert; - female subjects who are not nursing or pregnant at the time of enrolment (negative urine pregnancy test) and have no family planning within the first 3 months after enrolment. effective contraceptive measures have been taken within 2 weeks before inclusion. - during the whole follow-up period of the study, be able and willing to complete the whole prescribed study plan; self has ability to understand the study procedures, the informed consent & voluntarily sign an informed consent form and is able to comply with the requirements of the clinical study protocol.