- acute febrile illness with temperature higher than or equal to 100.4°f (38.0°c) or acute onset of upper or lower respiratory tract symptoms (e.g., cough, shortness of breath, sore throat). - positive serologic or molecular (reverse transcription polymerase chain reaction (rt-pcr)) test for sars-cov-2 at screening (this criterion applies to all phase 2 participants and only applies after approximately 402 participants positive for sars-cov-2 serologic test are randomized in the phase 3 segment of the study). - pregnant or breastfeeding or intending to become pregnant or intending to father children within the projected duration of the trial starting from the screening visit until 3 months following the last dose (phase 2) or until last dose (phase 3). - known history of uncontrolled hiv based on a cd4 count less than 200 cells per cubic millimeter (/mm^3) or a detectable viral load within the past 3 months. - is currently participating or has participated in a study with an investigational product within 30 days preceding day 0. - previous or planned receipt of an investigational (including emergency use authorization (eua) or local equivalent authorization) or licensed vaccine for prevention or treatment of covid-19, middle east respiratory syndrome (mers), or severe acute respiratory syndrome (sars) (documented receipt of placebo in previous trial would be permissible for trial eligibility). - respiratory diseases (e.g., asthma, chronic obstructive pulmonary disease) requiring significant changes in therapy or hospitalization for worsening disease during the 6 weeks prior to enrolment. - immunosuppression as a result of underlying illness or treatment. - lack of acceptable sites available for id injection and ep. - blood donation or transfusion within 1 month prior to day 0. - reported alcohol or substance abuse or dependence, or illicit drug use (excluding marijuana use). - any illness or condition that in the opinion of the investigator may affect the safety of the participant or the evaluation of any study endpoint.

- acute febrile illness with temperature higher than or equal to 100.4°f (38.0°c) or acute onset of upper or lower respiratory tract symptoms (e.g., cough, shortness of breath, sore throat). - positive serologic or molecular (reverse transcription polymerase chain reaction (rt-pcr)) test for sars-cov-2 at screening (this criterion applies to all phase 2 participants and only applies after approximately 402 participants positive for sars-cov-2 serologic test are randomized in the phase 3 segment of the study). - pregnant or breastfeeding or intending to become pregnant or intending to father children within the projected duration of the trial starting from the screening visit until 3 months following the last dose (phase 2) or until last dose (phase 3). - known history of uncontrolled hiv based on a cd4 count less than 200 cells per cubic millimeter (/mm^3) or a detectable viral load within the past 3 months. - is currently participating or has participated in a study with an investigational product within 30 days preceding day 0. - previous or planned receipt of an investigational (including emergency use authorization (eua) or local equivalent authorization) or licensed vaccine for prevention or treatment of covid-19, middle east respiratory syndrome (mers), or severe acute respiratory syndrome (sars) (documented receipt of placebo in previous trial would be permissible for trial eligibility). - respiratory diseases (e.g., asthma, chronic obstructive pulmonary disease) requiring significant changes in therapy or hospitalization for worsening disease during the 6 weeks prior to enrolment. - immunosuppression as a result of underlying illness or treatment. - lack of acceptable sites available for id injection and ep. - blood donation or transfusion within 1 month prior to day 0. - reported alcohol or substance abuse or dependence, or illicit drug use (excluding marijuana use). - any illness or condition that in the opinion of the investigator may affect the safety of the participant or the evaluation of any study endpoint.

- acute febrile illness with temperature higher than 100.4°f (38.0°c) or acute onset of upper or lower respiratory tract symptoms (e.g., cough, shortness of breath, sore throat). - positive serologic or molecular (reverse transcription polymerase chain reaction (rt-pcr)) test for sars-cov-2 at screening. - pregnant or breastfeeding or intending to become pregnant or intending to father children within the projected duration of the trial starting from the screening visit until 3 months following the last dose. - known history of uncontrolled hiv based on a cd4 count less than 200 cells per cubic millimeter (/mm^3) or a detectable viral load within the past 3 months. - is currently participating or has participated in a study with an investigational product within 30 days preceding day 0. - previous receipt of an investigational vaccine for prevention or treatment of covid-19, middle east respiratory syndrome (mers), or severe acute respiratory syndrome (sars) (documented receipt of placebo in previous trial would be permissible for trial eligibility). - respiratory diseases (e.g., asthma, chronic obstructive pulmonary disease) requiring significant changes in therapy or hospitalization for worsening disease during the 6 weeks prior to enrolment. - immunosuppression as a result of underlying illness or treatment. - lack of acceptable sites available for id injection and ep. - blood donation or transfusion within 1 month prior to day 0. - reported alcohol or substance abuse or dependence, or illicit drug use (excluding marijuana use). - any illness or condition that in the opinion of the investigator may affect the safety of the participant or the evaluation of any study endpoint.

- acute febrile illness with temperature higher than 100.4°f (38.0°c) or acute onset of upper or lower respiratory tract symptoms (e.g., cough, shortness of breath, sore throat). - positive serologic or molecular (reverse transcription polymerase chain reaction (rt-pcr)) test for sars-cov-2 at screening. - pregnant or breastfeeding or intending to become pregnant or intending to father children within the projected duration of the trial starting from the screening visit until 3 months following the last dose. - known history of uncontrolled hiv based on a cd4 count less than 200 cells per cubic millimeter (/mm^3) or a detectable viral load within the past 3 months. - is currently participating or has participated in a study with an investigational product within 30 days preceding day 0. - previous receipt of an investigational vaccine for prevention or treatment of covid-19, middle east respiratory syndrome (mers), or severe acute respiratory syndrome (sars) (documented receipt of placebo in previous trial would be permissible for trial eligibility). - respiratory diseases (e.g., asthma, chronic obstructive pulmonary disease) requiring significant changes in therapy or hospitalization for worsening disease during the 6 weeks prior to enrolment. - immunosuppression as a result of underlying illness or treatment. - lack of acceptable sites available for id injection and ep. - blood donation or transfusion within 1 month prior to day 0. - reported alcohol or substance abuse or dependence, or illicit drug use (excluding marijuana use). - any illness or condition that in the opinion of the investigator may affect the safety of the participant or the evaluation of any study endpoint.