* 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 human immunodeficiency virus (hiv) based on clusters of differentiation (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 human immunodeficiency virus (hiv) based on clusters of differentiation (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 human immunodeficiency virus (hiv) based on clusters of differentiation (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 human immunodeficiency virus (hiv) based on clusters of differentiation (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 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.