inclusion criteria: 1. adults aged 18 years and older; 2. vaccinated with 2 or 3 doses of marketed inactivated sars-cov-2 vaccine according to national immunization planning, whose last dose was given at least 6 months ago; 3. willing and able to comply with study requirements, and other study procedures within 6 months after vaccination; 4. female participants or partners of male participants of childbearing potential: from the first day of last menstruation cycle to the day of enrolment, must had no sexual behavior with a male or had effective contraceptive methods without failure; voluntarily agree to maintain abstinent or use effective contraception with their partners until 6 months after vaccination; 5. based on medical history enquiry, physical examination, and blood routine examination, the investigator judges the participants as in a healthy status; participants with mild underlying disease (for example chonic diseases like diabetes/hypertension/hyperlipemia, etc.) must be in a stable state without exacerbation (no admission to hospital or no major adjustment to treatment regimen, etc.) for at least 3 months prior to enrollment in this study. 6. understand the contents of the icf and voluntarily sign it.

inclusion criteria: 1. adults aged 18 years and older; 2. vaccinated with 2 or 3 doses of marketed inactivated sars-cov-2 vaccine according to national immunization planning, whose last dose was given at least 6 months ago; 3. willing and able to comply with study requirements, and other study procedures within 6 months after vaccination; 4. female participants or partners of male participants of childbearing potential: from the first day of last menstruation cycle to the day of enrolment, must had no sexual behavior with a male or had effective contraceptive methods without failure; voluntarily agree to maintain abstinent or use effective contraception with their partners until 6 months after vaccination; 5. based on medical history enquiry, physical examination, and blood routine examination, the investigator judges the participants as in a healthy status; participants with mild underlying disease (for example chonic diseases like diabetes/hypertension/hyperlipemia, etc.) must be in a stable state without exacerbation (no admission to hospital or no major adjustment to treatment regimen, etc.) for at least 3 months prior to enrollment in this study. 6. understand the contents of the icf and voluntarily sign it.

inclusion criteria: adults aged 18 years and older; vaccinated with 2 or 3 doses of marketed inactivated sars-cov-2 vaccine according to national immunization planning, whose last dose was given at least 6 months ago; willing and able to comply with study requirements, and other study procedures within 6 months after vaccination; female participants or partners of male participants of childbearing potential: from the first day of last menstruation cycle to the day of enrolment, must had no sexual behavior with a male or had effective contraceptive methods without failure; voluntarily agree to maintain abstinent or use effective contraception with their partners until 6 months after vaccination; based on medical history enquiry, physical examination, and blood routine examination, the investigator judges the participants as in a healthy status; participants with mild underlying disease (for example chonic diseases like diabetes/hypertension/hyperlipemia, etc.) must be in a stable state without exacerbation (no admission to hospital or no major adjustment to treatment regimen, etc.) for at least 3 months prior to enrollment in this study. understand the contents of the icf and voluntarily sign it.

inclusion criteria: adults aged 18 years and older; vaccinated with 2 or 3 doses of marketed inactivated sars-cov-2 vaccine according to national immunization planning, whose last dose was given at least 6 months ago; willing and able to comply with study requirements, and other study procedures within 6 months after vaccination; female participants or partners of male participants of childbearing potential: from the first day of last menstruation cycle to the day of enrolment, must had no sexual behavior with a male or had effective contraceptive methods without failure; voluntarily agree to maintain abstinent or use effective contraception with their partners until 6 months after vaccination; based on medical history enquiry, physical examination, and blood routine examination, the investigator judges the participants as in a healthy status; participants with mild underlying disease (for example chonic diseases like diabetes/hypertension/hyperlipemia, etc.) must be in a stable state without exacerbation (no admission to hospital or no major adjustment to treatment regimen, etc.) for at least 3 months prior to enrollment in this study. understand the contents of the icf and voluntarily sign it.