inclusion criteria: aged 18 to 60 years (included) at screening. have a body mass index (bmi) between 18.5 and 35.0 kg/m2 (included) able and willing to comply with all study requirements. willing to allow the investigator to discuss the volunteers'participant's medical history with his/her general practitioner/personal doctors and access all medical records which are relevant to study procedures. participants who are of general good health, or with medically stable, well-controlled comorbidities according to the investigator's assessment, based on medical history at the time of screening and clinical evaluations. have completed three doses vaccination by any mrna covid-19 vaccine 3~12 months (90~365 days, included) prior to the study vaccination. females of childbearing potential who are involved in heterosexual sexual activity, must be willing to practice continuous effective contraception until 90 days after the study vaccination and have negative pregnancy tests before study vaccination. nonchildbearing potential is defined as surgically sterile (history of bilateral tubal ligation, bilateral oophorectomy, hysterectomy) or postmenopausal (defined as amenorrhea for ≥ 12 consecutive months prior to screening without an alternative medical cause). a follicle-stimulating hormone (fsh) level may be measured at the discretion of the investigator to confirm postmenopausal status. the effective contraceptive methods include sexual abstinence or adequate contraceptive measures such as intrauterine or implanted contraceptive device, oral contraceptives, injected or implanted contraceptives, sustained-release topical contraceptives, condoms (male), diaphragm, and cervical cap, etc. males participating in this study who are involved in heterosexual sexual activity must agree to practice adequate contraception (as described above) and refrain from donating sperm until 90 days after the study vaccination. agreement to refrain from blood donation during the study from time of informed consent until end of study visit. provide written informed consent form (icf) prior to any study screening activity.

inclusion criteria: aged 18 to 60 years (included) at screening. have a body mass index (bmi) between 18.5 and 35.0 kg/m2 (included) able and willing to comply with all study requirements. willing to allow the investigator to discuss the volunteers'participant's medical history with his/her general practitioner/personal doctors and access all medical records which are relevant to study procedures. participants who are of general good health, or with medically stable, well-controlled comorbidities according to the investigator's assessment, based on medical history at the time of screening and clinical evaluations. have completed three doses vaccination by any mrna covid-19 vaccine 3~12 months (90~365 days, included) prior to the study vaccination. females of childbearing potential who are involved in heterosexual sexual activity, must be willing to practice continuous effective contraception until 90 days after the study vaccination and have negative pregnancy tests before study vaccination. nonchildbearing potential is defined as surgically sterile (history of bilateral tubal ligation, bilateral oophorectomy, hysterectomy) or postmenopausal (defined as amenorrhea for ≥ 12 consecutive months prior to screening without an alternative medical cause). a follicle-stimulating hormone (fsh) level may be measured at the discretion of the investigator to confirm postmenopausal status. the effective contraceptive methods include sexual abstinence or adequate contraceptive measures such as intrauterine or implanted contraceptive device, oral contraceptives, injected or implanted contraceptives, sustained-release topical contraceptives, condoms (male), diaphragm, and cervical cap, etc. males participating in this study who are involved in heterosexual sexual activity must agree to practice adequate contraception (as described above) and refrain from donating sperm until 90 days after the study vaccination. agreement to refrain from blood donation during the study from time of informed consent until end of study visit. provide written informed consent form (icf) prior to any study screening activity.