inclusion criteria: 1. able and willing to comply with all study requirements. 2. give informed consent and sign informed consent form (icf). for subjects who are unable to read or write, the consent must be witnessed by a literate third party not involved in the study. 3. bmi in between 18.5 and 30.0 kg/m2 (including upper and lower limits). 4. for each group, meet the following criteria regarding age, covid-19 vaccination history (as confirmed by covid-19 vaccination records), and sars-cov-2 infection history (as confirmed by the investigator according to who definitions, appendix iii): group 1: adult-coronavac® group - aged 18-59 and received 2 to 4 homologous doses of coronavac® at least 3 months prior to enrollment and without sars-cov-2 infection history. group 2: adult-comirnaty® group - aged 18-59 and received 2 to 4 heterologous doses of coronavac® and comirnaty® at least 3 months prior to enrollment and without sars-cov-2 infection history; or group 3: adult-mixed group * aged 18-59 and received 2 to 4 heterologous doses of coronavac® and comirnaty® at least 3 months prior to enrollment and without sars-cov-2 infection history; or * aged 18-59 and received 2 to 4 heterologous doses of coronavac® and comirnaty® at least 3 months prior to enrollment and recovered from sars-cov-2 infection at least 3 months prior to enrollment; or * aged 18-59 and received 2 to 4 homologous doses of coronavac® or comirnaty® at least 3 months prior to enrollment and recovered from sars-cov-2 infection at least 3 months prior to enrollment. group 4: elderly-mixed group * aged 60-75 and received 2 to 4 heterologous doses of coronavac® and comirnaty® at least 3 months prior to enrollment and without sars-cov-2 infection history; or * aged 60-75 and received 2 to 4 heterologous doses of coronavac® and comirnaty® at least 3 months prior to enrollment and recovered from sars-cov-2 infection at least 3 months prior to enrollment; or * aged 60-75 and received 2 to 4 homologous doses of coronavac® or comirnaty® at least 3 months prior to enrollment and without sars-cov-2 infection history; or * aged 60-75 and received 2 to 4 homologous doses of coronavac® or comirnaty® at least 3 months prior to enrollment and recovered from sars-cov-2 infection at least 3 months prior to enrollment. 5. healthy subjects, or subjects with stable medical condition who have a pre-existing medical condition that does not meet any exclusion criteria. a stable medical condition is defined as disease not requiring significant change in therapy or hospitalization for worsening disease during the 3 months prior to enrollment. 6. female subjects of childbearing potential with have negative pregnancy test shall be willing to practice continuous effective contraception and not to breastfeed until 12 months after iccov administration. * nonchildbearing potential is defined as surgically sterile (history of bilateral tubal ligation, bilateral oophorectomy, hysterectomy) or postmenopausal. a follicle-stimulating hormone (fsh) level and the amenorrhea duration (e.g., amenorrhea for ≥ 12 consecutive months prior to screening without an alternative medical cause) 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. 7. male subjects who are involved in heterosexual sexual activity must agree to practice adequate contraception (as described above) and refrain from donating sperm until 12 months after iccov administration. 8. agreement to avoid blood donation during the study.

inclusion criteria: 1. able and willing to comply with all study requirements. 2. give informed consent and sign informed consent form (icf). for subjects who are unable to read or write, the consent must be witnessed by a literate third party not involved in the study. 3. bmi in between 18.5 and 30.0 kg/m2 (including upper and lower limits). 4. for each group, meet the following criteria regarding age, covid-19 vaccination history (as confirmed by covid-19 vaccination records), and sars-cov-2 infection history (as confirmed by the investigator according to who definitions, appendix iii): group 1: adult-coronavac® group - aged 18-59 and received 2 to 4 homologous doses of coronavac® at least 3 months prior to enrollment and without sars-cov-2 infection history. group 2: adult-comirnaty® group - aged 18-59 and received 2 to 4 heterologous doses of coronavac® and comirnaty® at least 3 months prior to enrollment and without sars-cov-2 infection history; or group 3: adult-mixed group * aged 18-59 and received 2 to 4 heterologous doses of coronavac® and comirnaty® at least 3 months prior to enrollment and without sars-cov-2 infection history; or * aged 18-59 and received 2 to 4 heterologous doses of coronavac® and comirnaty® at least 3 months prior to enrollment and recovered from sars-cov-2 infection at least 3 months prior to enrollment; or * aged 18-59 and received 2 to 4 homologous doses of coronavac® or comirnaty® at least 3 months prior to enrollment and recovered from sars-cov-2 infection at least 3 months prior to enrollment. group 4: elderly-mixed group * aged 60-75 and received 2 to 4 heterologous doses of coronavac® and comirnaty® at least 3 months prior to enrollment and without sars-cov-2 infection history; or * aged 60-75 and received 2 to 4 heterologous doses of coronavac® and comirnaty® at least 3 months prior to enrollment and recovered from sars-cov-2 infection at least 3 months prior to enrollment; or * aged 60-75 and received 2 to 4 homologous doses of coronavac® or comirnaty® at least 3 months prior to enrollment and without sars-cov-2 infection history; or * aged 60-75 and received 2 to 4 homologous doses of coronavac® or comirnaty® at least 3 months prior to enrollment and recovered from sars-cov-2 infection at least 3 months prior to enrollment. 5. healthy subjects, or subjects with stable medical condition who have a pre-existing medical condition that does not meet any exclusion criteria. a stable medical condition is defined as disease not requiring significant change in therapy or hospitalization for worsening disease during the 3 months prior to enrollment. 6. female subjects of childbearing potential with have negative pregnancy test shall be willing to practice continuous effective contraception and not to breastfeed until 12 months after iccov administration. * nonchildbearing potential is defined as surgically sterile (history of bilateral tubal ligation, bilateral oophorectomy, hysterectomy) or postmenopausal. a follicle-stimulating hormone (fsh) level and the amenorrhea duration (e.g., amenorrhea for ≥ 12 consecutive months prior to screening without an alternative medical cause) 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. 7. male subjects who are involved in heterosexual sexual activity must agree to practice adequate contraception (as described above) and refrain from donating sperm until 12 months after iccov administration. 8. agreement to avoid blood donation during the study.

inclusion criteria: able and willing to comply with all study requirements. give informed consent and sign informed consent form (icf). for subjects who are unable to read or write, the consent must be witnessed by a literate third party not involved in the study. bmi in between 18.5 and 30.0 kg/m2 (including upper and lower limits). for each group, meet the following criteria regarding age, covid-19 vaccination history (as confirmed by covid-19 vaccination records), and sars-cov-2 infection history (as confirmed by the investigator according to who definitions, appendix iii): group 1: adult-coronavac® group - aged 18-59 and received 2 to 4 homologous doses of coronavac® at least 3 months prior to enrollment and without sars-cov-2 infection history. group 2: adult-comirnaty® group - aged 18-59 and received 2 to 4 heterologous doses of coronavac® and comirnaty® at least 3 months prior to enrollment and without sars-cov-2 infection history; or group 3: adult-mixed group aged 18-59 and received 2 to 4 heterologous doses of coronavac® and comirnaty® at least 3 months prior to enrollment and without sars-cov-2 infection history; or aged 18-59 and received 2 to 4 heterologous doses of coronavac® and comirnaty® at least 3 months prior to enrollment and recovered from sars-cov-2 infection at least 3 months prior to enrollment; or aged 18-59 and received 2 to 4 homologous doses of coronavac® or comirnaty® at least 3 months prior to enrollment and recovered from sars-cov-2 infection at least 3 months prior to enrollment. group 4: elderly-mixed group aged 60-75 and received 2 to 4 heterologous doses of coronavac® and comirnaty® at least 3 months prior to enrollment and without sars-cov-2 infection history; or aged 60-75 and received 2 to 4 heterologous doses of coronavac® and comirnaty® at least 3 months prior to enrollment and recovered from sars-cov-2 infection at least 3 months prior to enrollment; or aged 60-75 and received 2 to 4 homologous doses of coronavac® or comirnaty® at least 3 months prior to enrollment and without sars-cov-2 infection history; or aged 60-75 and received 2 to 4 homologous doses of coronavac® or comirnaty® at least 3 months prior to enrollment and recovered from sars-cov-2 infection at least 3 months prior to enrollment. healthy subjects, or subjects with stable medical condition who have a pre-existing medical condition that does not meet any exclusion criteria. a stable medical condition is defined as disease not requiring significant change in therapy or hospitalization for worsening disease during the 3 months prior to enrollment. female subjects of childbearing potential with have negative pregnancy test shall be willing to practice continuous effective contraception and not to breastfeed until 12 months after iccov administration. nonchildbearing potential is defined as surgically sterile (history of bilateral tubal ligation, bilateral oophorectomy, hysterectomy) or postmenopausal. a follicle-stimulating hormone (fsh) level and the amenorrhea duration (e.g., amenorrhea for ≥ 12 consecutive months prior to screening without an alternative medical cause) 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. male subjects who are involved in heterosexual sexual activity must agree to practice adequate contraception (as described above) and refrain from donating sperm until 12 months after iccov administration. agreement to avoid blood donation during the study.

inclusion criteria: able and willing to comply with all study requirements. give informed consent and sign informed consent form (icf). for subjects who are unable to read or write, the consent must be witnessed by a literate third party not involved in the study. bmi in between 18.5 and 30.0 kg/m2 (including upper and lower limits). for each group, meet the following criteria regarding age, covid-19 vaccination history (as confirmed by covid-19 vaccination records), and sars-cov-2 infection history (as confirmed by the investigator according to who definitions, appendix iii): group 1: adult-coronavac® group - aged 18-59 and received 2 to 4 homologous doses of coronavac® at least 3 months prior to enrollment and without sars-cov-2 infection history. group 2: adult-comirnaty® group - aged 18-59 and received 2 to 4 heterologous doses of coronavac® and comirnaty® at least 3 months prior to enrollment and without sars-cov-2 infection history; or group 3: adult-mixed group aged 18-59 and received 2 to 4 heterologous doses of coronavac® and comirnaty® at least 3 months prior to enrollment and without sars-cov-2 infection history; or aged 18-59 and received 2 to 4 heterologous doses of coronavac® and comirnaty® at least 3 months prior to enrollment and recovered from sars-cov-2 infection at least 3 months prior to enrollment; or aged 18-59 and received 2 to 4 homologous doses of coronavac® or comirnaty® at least 3 months prior to enrollment and recovered from sars-cov-2 infection at least 3 months prior to enrollment. group 4: elderly-mixed group aged 60-75 and received 2 to 4 heterologous doses of coronavac® and comirnaty® at least 3 months prior to enrollment and without sars-cov-2 infection history; or aged 60-75 and received 2 to 4 heterologous doses of coronavac® and comirnaty® at least 3 months prior to enrollment and recovered from sars-cov-2 infection at least 3 months prior to enrollment; or aged 60-75 and received 2 to 4 homologous doses of coronavac® or comirnaty® at least 3 months prior to enrollment and without sars-cov-2 infection history; or aged 60-75 and received 2 to 4 homologous doses of coronavac® or comirnaty® at least 3 months prior to enrollment and recovered from sars-cov-2 infection at least 3 months prior to enrollment. healthy subjects, or subjects with stable medical condition who have a pre-existing medical condition that does not meet any exclusion criteria. a stable medical condition is defined as disease not requiring significant change in therapy or hospitalization for worsening disease during the 3 months prior to enrollment. female subjects of childbearing potential with have negative pregnancy test shall be willing to practice continuous effective contraception and not to breastfeed until 12 months after iccov administration. nonchildbearing potential is defined as surgically sterile (history of bilateral tubal ligation, bilateral oophorectomy, hysterectomy) or postmenopausal. a follicle-stimulating hormone (fsh) level and the amenorrhea duration (e.g., amenorrhea for ≥ 12 consecutive months prior to screening without an alternative medical cause) 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. male subjects who are involved in heterosexual sexual activity must agree to practice adequate contraception (as described above) and refrain from donating sperm until 12 months after iccov administration. agreement to avoid blood donation during the study.