inclusion criteria: * healthy adults aged 18 years and above; * have been received two doses of inactivated sars-cov-2 vaccine(coronavac)manufactured by sinovac research \& development co., ltd at an interval of 6 months or more; * participants should be capable of understanding the informed consent form, and such form should be signed prior to enrolment ; * proven legal identity;

inclusion criteria: * healthy adults aged 18 years and above; * have been received two doses of inactivated sars-cov-2 vaccine(coronavac)manufactured by sinovac research \& development co., ltd at an interval of 6 months or more; * participants should be capable of understanding the informed consent form, and such form should be signed prior to enrolment ; * proven legal identity;

inclusion criteria: healthy adults aged 18 years and above; have been received two doses of inactivated sars-cov-2 vaccine(coronavac)manufactured by sinovac research & development co., ltd at an interval of 6 months or more; participants should be capable of understanding the informed consent form, and such form should be signed prior to enrolment ; proven legal identity;

inclusion criteria: healthy adults aged 18 years and above; have been received two doses of inactivated sars-cov-2 vaccine(coronavac)manufactured by sinovac research & development co., ltd at an interval of 6 months or more; participants should be capable of understanding the informed consent form, and such form should be signed prior to enrolment ; proven legal identity;