inclusion criteria: 1. adults aged 18 years and older. 2. understand the content of the informed consent form (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). 3. participants who are willing and able to comply with study requirements, including all scheduled visits, vaccinations, laboratory tests, and other study procedures. 4. female participants of childbearing potential or partners of male participants: voluntarily agree to use effective contraception with their partners prior to the first vaccination and must agree to continue such precautions during the study until 3 months after full vaccination (including the initial set of vaccination and crossover set of vaccination). \[effective contraception includes oral contraceptives, injectable or implantable contraception, extended-release topical contraceptives, hormonal patches, intrauterine devices (iuds), sterilization, abstinence, condoms (for male), diaphragms, cervical caps, etc.\]. 5. 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 vaccination in this study. 6. on the day of 1st dose of vaccination and 24 hours prior to vaccination, axillary temperatures \<37.3°c/99.1°f. 7. healthy participants or participants with mild underlying disease \[in a stable state without exacerbation (no admission to hospital or no major adjustment to treatment regimen, etc.) for at least 3 months prior to enrollment in this study\].

inclusion criteria: 1. adults aged 18 years and older. 2. understand the content of the informed consent form (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). 3. participants who are willing and able to comply with study requirements, including all scheduled visits, vaccinations, laboratory tests, and other study procedures. 4. female participants of childbearing potential or partners of male participants: voluntarily agree to use effective contraception with their partners prior to the first vaccination and must agree to continue such precautions during the study until 3 months after full vaccination (including the initial set of vaccination and crossover set of vaccination). \[effective contraception includes oral contraceptives, injectable or implantable contraception, extended-release topical contraceptives, hormonal patches, intrauterine devices (iuds), sterilization, abstinence, condoms (for male), diaphragms, cervical caps, etc.\]. 5. 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 vaccination in this study. 6. on the day of 1st dose of vaccination and 24 hours prior to vaccination, axillary temperatures \<37.3°c/99.1°f. 7. healthy participants or participants with mild underlying disease \[in a stable state without exacerbation (no admission to hospital or no major adjustment to treatment regimen, etc.) for at least 3 months prior to enrollment in this study\].

inclusion criteria: adults aged 18 years and older. understand the content of the informed consent form (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 study requirements, including all scheduled visits, vaccinations, laboratory tests, 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 first vaccination and must agree to continue such precautions during the study until 3 months after full vaccination (including the initial set of vaccination and crossover set of 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 vaccination in this study. on the day of 1st dose of vaccination and 24 hours prior to vaccination, axillary temperatures <37.3°c/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].

inclusion criteria: adults aged 18 years and older. understand the content of the informed consent form (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 study requirements, including all scheduled visits, vaccinations, laboratory tests, 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 first vaccination and must agree to continue such precautions during the study until 3 months after full vaccination (including the initial set of vaccination and crossover set of 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 vaccination in this study. on the day of 1st dose of vaccination and 24 hours prior to vaccination, axillary temperatures <37.3°c/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].