inclusion criteria: * adults aged 18 years and older. * understand the content of the icf, and voluntarily sign the icf (if the participant is unable to sign the icf on his/her own due to illiteracy, an impartial witness is needed). * participants who are willing and able to comply with all scheduled visits, vaccination plan, laboratory tests, lifestyle considerations, and other study procedures. * female participants of childbearing potential or partners of male participants: voluntarily agree to use effective contraception with their partners prior to the (1st dose of) vaccination and must agree to continue such precautions during the study until 3 months after (full) vaccination.\[effective contraception includes oral contraceptives, injectable or implantable contraception, extended-release topical contraceptives, hormonal patches, intrauterine devices(iuds), sterilization, abstinence, condoms (for male), diaphragms, cervical caps, etc.\]. * for female participants: without childbearing potential (amenorrhea for at least 1 year or documented surgical sterilization) or have used effective contraception with a negative pregnancy test before (each dose of) vaccination in this study. * on the day of vaccination and 24 hours prior to (each dose of) vaccination, axillary temperatures\<37.3℃/99.1°f. * healthy participants or participants with mild underlying disease \[in a stable state without exacerbation (no admission to hospital or no major adjustment to treatment regimen, etc.) for at least 3 months prior to enrollment in this study\]. * (for group 2 and group 3 only) participants who have received full primary vaccination of licensed sars-cov-2 vaccine (3-8 weeks between 2 doses of covid-19 inactivated vaccine or 2 doses of covid-19 mrna vaccine) and whose last dose was given \>6 mony * (for group 1 only) not have received any covid-19 vaccine prior to enrollment.

inclusion criteria: * adults aged 18 years and older. * understand the content of the icf, and voluntarily sign the icf (if the participant is unable to sign the icf on his/her own due to illiteracy, an impartial witness is needed). * participants who are willing and able to comply with all scheduled visits, vaccination plan, laboratory tests, lifestyle considerations, and other study procedures. * female participants of childbearing potential or partners of male participants: voluntarily agree to use effective contraception with their partners prior to the (1st dose of) vaccination and must agree to continue such precautions during the study until 3 months after (full) vaccination.\[effective contraception includes oral contraceptives, injectable or implantable contraception, extended-release topical contraceptives, hormonal patches, intrauterine devices(iuds), sterilization, abstinence, condoms (for male), diaphragms, cervical caps, etc.\]. * for female participants: without childbearing potential (amenorrhea for at least 1 year or documented surgical sterilization) or have used effective contraception with a negative pregnancy test before (each dose of) vaccination in this study. * on the day of vaccination and 24 hours prior to (each dose of) vaccination, axillary temperatures\<37.3℃/99.1°f. * healthy participants or participants with mild underlying disease \[in a stable state without exacerbation (no admission to hospital or no major adjustment to treatment regimen, etc.) for at least 3 months prior to enrollment in this study\]. * (for group 2 and group 3 only) participants who have received full primary vaccination of licensed sars-cov-2 vaccine (3-8 weeks between 2 doses of covid-19 inactivated vaccine or 2 doses of covid-19 mrna vaccine) and whose last dose was given \>6 mony * (for group 1 only) not have received any covid-19 vaccine prior to enrollment.

inclusion criteria: adults aged 18 years and older. understand the content of the icf, and voluntarily sign the icf (if the participant is unable to sign the icf on his/her own due to illiteracy, an impartial witness is needed). participants who are willing and able to comply with all scheduled visits, vaccination plan, laboratory tests, lifestyle considerations, and other study procedures. female participants of childbearing potential or partners of male participants: voluntarily agree to use effective contraception with their partners prior to the (1st dose of) vaccination and must agree to continue such precautions during the study until 3 months after (full) vaccination.[effective contraception includes oral contraceptives, injectable or implantable contraception, extended-release topical contraceptives, hormonal patches, intrauterine devices(iuds), sterilization, abstinence, condoms (for male), diaphragms, cervical caps, etc.]. for female participants: without childbearing potential (amenorrhea for at least 1 year or documented surgical sterilization) or have used effective contraception with a negative pregnancy test before (each dose of) vaccination in this study. on the day of vaccination and 24 hours prior to (each dose of) vaccination, axillary temperatures<37.3℃/99.1°f. healthy participants or participants with mild underlying disease [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]. (for group 2 and group 3 only) participants who have received full primary vaccination of licensed sars-cov-2 vaccine (3-8 weeks between 2 doses of covid-19 inactivated vaccine or 2 doses of covid-19 mrna vaccine) and whose last dose was given >6 mony (for group 1 only) not have received any covid-19 vaccine prior to enrollment.

inclusion criteria: adults aged 18 years and older. understand the content of the icf, and voluntarily sign the icf (if the participant is unable to sign the icf on his/her own due to illiteracy, an impartial witness is needed). participants who are willing and able to comply with all scheduled visits, vaccination plan, laboratory tests, lifestyle considerations, and other study procedures. female participants of childbearing potential or partners of male participants: voluntarily agree to use effective contraception with their partners prior to the (1st dose of) vaccination and must agree to continue such precautions during the study until 3 months after (full) vaccination.[effective contraception includes oral contraceptives, injectable or implantable contraception, extended-release topical contraceptives, hormonal patches, intrauterine devices(iuds), sterilization, abstinence, condoms (for male), diaphragms, cervical caps, etc.]. for female participants: without childbearing potential (amenorrhea for at least 1 year or documented surgical sterilization) or have used effective contraception with a negative pregnancy test before (each dose of) vaccination in this study. on the day of vaccination and 24 hours prior to (each dose of) vaccination, axillary temperatures<37.3℃/99.1°f. healthy participants or participants with mild underlying disease [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]. (for group 2 and group 3 only) participants who have received full primary vaccination of licensed sars-cov-2 vaccine (3-8 weeks between 2 doses of covid-19 inactivated vaccine or 2 doses of covid-19 mrna vaccine) and whose last dose was given >6 mony (for group 1 only) not have received any covid-19 vaccine prior to enrollment.