individuals who: 1. are unable to comply with the study visits or procedures in study arct-021-01 2. received placebo in the parent study and who are not willing to receive arct-021 in this study. only for subjects that will receive arct-021 in this study: 3. have or will receive any of the sars cov-2 or another experimental coronavirus during this study. 4. have a diagnosis of new clinically significant abnormalities including but not limited to * respiratory disease requiring daily medications or oxygen currently or any treatment of respiratory disease exacerbations * significant heart conditions * significant neurological conditions * significant blood disorders * newly diagnosed autoimmune disease * major surgery 5. have abnormal screening laboratory results 6. have uncontrolled diabetes 7. use of any prescription or over-the-counter medications within 7 days prior to vaccination 8. have received immunoglobulins and/or any blood or blood products 9. have a bleeding disorder 10. have uncontrolled blood pressure 11. have been treated with another investigational drug, biological agent, or device since completion of the parent study 12. have received or plan to receive: * a licensed, live vaccine within 4 weeks before or after study vaccination, or * a licensed, inactivated vaccine within 2 weeks before or after study vaccination 13. have traveled outside of singapore within 30 days before the vaccination or plans to travel outside of singapore within 60 days after vaccination. 14. other restrictions may apply

individuals who: 1. are unable to comply with the study visits or procedures in study arct-021-01 2. received placebo in the parent study and who are not willing to receive arct-021 in this study. only for subjects that will receive arct-021 in this study: 3. have or will receive any of the sars cov-2 or another experimental coronavirus during this study. 4. have a diagnosis of new clinically significant abnormalities including but not limited to * respiratory disease requiring daily medications or oxygen currently or any treatment of respiratory disease exacerbations * significant heart conditions * significant neurological conditions * significant blood disorders * newly diagnosed autoimmune disease * major surgery 5. have abnormal screening laboratory results 6. have uncontrolled diabetes 7. use of any prescription or over-the-counter medications within 7 days prior to vaccination 8. have received immunoglobulins and/or any blood or blood products 9. have a bleeding disorder 10. have uncontrolled blood pressure 11. have been treated with another investigational drug, biological agent, or device since completion of the parent study 12. have received or plan to receive: * a licensed, live vaccine within 4 weeks before or after study vaccination, or * a licensed, inactivated vaccine within 2 weeks before or after study vaccination 13. have traveled outside of singapore within 30 days before the vaccination or plans to travel outside of singapore within 60 days after vaccination. 14. other restrictions may apply

individuals who: are unable to comply with the study visits or procedures in study arct-021-01 received placebo in the parent study and who are not willing to receive arct-021 in this study. only for subjects that will receive arct-021 in this study: have or will receive any of the sars cov-2 or another experimental coronavirus during this study. have a diagnosis of new clinically significant abnormalities including but not limited to respiratory disease requiring daily medications or oxygen currently or any treatment of respiratory disease exacerbations significant heart conditions significant neurological conditions significant blood disorders newly diagnosed autoimmune disease major surgery have abnormal screening laboratory results have uncontrolled diabetes use of any prescription or over-the-counter medications within 7 days prior to vaccination have received immunoglobulins and/or any blood or blood products have a bleeding disorder have uncontrolled blood pressure have been treated with another investigational drug, biological agent, or device since completion of the parent study have received or plan to receive: a licensed, live vaccine within 4 weeks before or after study vaccination, or a licensed, inactivated vaccine within 2 weeks before or after study vaccination have traveled outside of singapore within 30 days before the vaccination or plans to travel outside of singapore within 60 days after vaccination. other restrictions may apply

individuals who: are unable to comply with the study visits or procedures in study arct-021-01 received placebo in the parent study and who are not willing to receive arct-021 in this study. only for subjects that will receive arct-021 in this study: have or will receive any of the sars cov-2 or another experimental coronavirus during this study. have a diagnosis of new clinically significant abnormalities including but not limited to respiratory disease requiring daily medications or oxygen currently or any treatment of respiratory disease exacerbations significant heart conditions significant neurological conditions significant blood disorders newly diagnosed autoimmune disease major surgery have abnormal screening laboratory results have uncontrolled diabetes use of any prescription or over-the-counter medications within 7 days prior to vaccination have received immunoglobulins and/or any blood or blood products have a bleeding disorder have uncontrolled blood pressure have been treated with another investigational drug, biological agent, or device since completion of the parent study have received or plan to receive: a licensed, live vaccine within 4 weeks before or after study vaccination, or a licensed, inactivated vaccine within 2 weeks before or after study vaccination have traveled outside of singapore within 30 days before the vaccination or plans to travel outside of singapore within 60 days after vaccination. other restrictions may apply

individuals who: 1. are unable to comply with the study visits or procedures in study arct-021-01 2. received placebo in the parent study and who are not willing to receive arct-021 in this study. only for subjects that will receive arct-021 in this study: 3. have or will receive any of the sars cov-2 or another experimental coronavirus during this study. 4. have a diagnosis of new clinically significant abnormalities including but not limited to - respiratory disease requiring daily medications or oxygen currently or any treatment of respiratory disease exacerbations - significant heart conditions - significant neurological conditions - significant blood disorders - newly diagnosed autoimmune disease - major surgery 5. have abnormal screening laboratory results 6. have uncontrolled diabetes 7. use of any prescription or over-the-counter medications within 7 days prior to vaccination 8. have received immunoglobulins and/or any blood or blood products 9. have a bleeding disorder 10. have uncontrolled blood pressure 11. have been treated with another investigational drug, biological agent, or device since completion of the parent study 12. have received or plan to receive: - a licensed, live vaccine within 4 weeks before or after study vaccination, or - a licensed, inactivated vaccine within 2 weeks before or after study vaccination 13. have traveled outside of singapore within 30 days before the vaccination or plans to travel outside of singapore within 60 days after vaccination. 14. other restrictions may apply

individuals who: 1. are unable to comply with the study visits or procedures in study arct-021-01 2. received placebo in the parent study and who are not willing to receive arct-021 in this study. only for subjects that will receive arct-021 in this study: 3. have or will receive any of the sars cov-2 or another experimental coronavirus during this study. 4. have a diagnosis of new clinically significant abnormalities including but not limited to - respiratory disease requiring daily medications or oxygen currently or any treatment of respiratory disease exacerbations - significant heart conditions - significant neurological conditions - significant blood disorders - newly diagnosed autoimmune disease - major surgery 5. have abnormal screening laboratory results 6. have uncontrolled diabetes 7. use of any prescription or over-the-counter medications within 7 days prior to vaccination 8. have received immunoglobulins and/or any blood or blood products 9. have a bleeding disorder 10. have uncontrolled blood pressure 11. have been treated with another investigational drug, biological agent, or device since completion of the parent study 12. have received or plan to receive: - a licensed, live vaccine within 4 weeks before or after study vaccination, or - a licensed, inactivated vaccine within 2 weeks before or after study vaccination 13. have traveled outside of singapore within 30 days before the vaccination or plans to travel outside of singapore within 60 days after vaccination. 14. other restrictions may apply