inclusion criteria: 1. adult males or females aged 18 years and above at the time of consent 2. healthy subjects in normal medical condition as determined by medical history, physical examination, and investigator's discretion 3. have previously received homologous full-dose of covid-19 vaccine authorized for emergency use, and at least 3 months post second vaccination prior to day 1 4. negative results for sars-cov-2 rapid antigen test at the screening period 5. able to comply with all study procedures and requirements 6. agree for blood and nasal swab samples could be collected throughout the study period, including surveillance visit

inclusion criteria: 1. adult males or females aged 18 years and above at the time of consent 2. healthy subjects in normal medical condition as determined by medical history, physical examination, and investigator's discretion 3. have previously received homologous full-dose of covid-19 vaccine authorized for emergency use, and at least 3 months post second vaccination prior to day 1 4. negative results for sars-cov-2 rapid antigen test at the screening period 5. able to comply with all study procedures and requirements 6. agree for blood and nasal swab samples could be collected throughout the study period, including surveillance visit

inclusion criteria: adult males or females aged 18 years and above at the time of consent healthy subjects in normal medical condition as determined by medical history, physical examination, and investigator's discretion have previously received homologous full-dose of covid-19 vaccine authorized for emergency use, and at least 3 months post second vaccination prior to day 1 negative results for sars-cov-2 rapid antigen test at the screening period able to comply with all study procedures and requirements agree for blood and nasal swab samples could be collected throughout the study period, including surveillance visit

inclusion criteria: adult males or females aged 18 years and above at the time of consent healthy subjects in normal medical condition as determined by medical history, physical examination, and investigator's discretion have previously received homologous full-dose of covid-19 vaccine authorized for emergency use, and at least 3 months post second vaccination prior to day 1 negative results for sars-cov-2 rapid antigen test at the screening period able to comply with all study procedures and requirements agree for blood and nasal swab samples could be collected throughout the study period, including surveillance visit

inclusion criteria: 1. adult males or females aged 18 years and above at the time of consent 2. healthy subjects in normal medical condition as determined by medical history, physical examination, and investigator's discretion 3. have previously received homologous full-dose of covid-19 vaccine authorized for emergency use, and at least 3 months post second vaccination prior to day 1 4. negative results for sars-cov-2 rapid antigen test at the screening period 5. able to comply with all study procedures and requirements 6. agree for blood and nasal swab samples could be collected throughout the study period, including surveillance visit

inclusion criteria: 1. adult males or females aged 18 years and above at the time of consent 2. healthy subjects in normal medical condition as determined by medical history, physical examination, and investigator's discretion 3. have previously received homologous full-dose of covid-19 vaccine authorized for emergency use, and at least 3 months post second vaccination prior to day 1 4. negative results for sars-cov-2 rapid antigen test at the screening period 5. able to comply with all study procedures and requirements 6. agree for blood and nasal swab samples could be collected throughout the study period, including surveillance visit