* have known allergies to any of the components used in the formulation of the scta01/placebo; * participants with a history of severe anaphylaxis, such as severe anaphylactic reaction, urticaria, and angioedema; * have spo2 ≤ 93% on room air at sea level or pao2/fio2 \< 300, respiratory rate ≥30 per minute, heart rate ≥125 per minute (fda); * require mechanical ventilation or anticipated impending need for mechanical ventilation; * suspected or proven serious bacterial, fungal, viral, or other infection (besides covid-19) that in the opinion of the investigator could constitute a risk when taking part in this study; * have any serious concomitant systemic disease, condition or disorder that, in the opinion of the investigator, should preclude participation in this study; * have any co-morbidity requiring surgery within \<29 days, or that is considered life threatening within 29 days; * have a history of previous sars-cov-2 infection; * received convalescent plasma, covid-19 vaccine, or anti-sars-cov-2 spike(s) protein targeted therapy; * have participated in a clinical study involving an investigational intervention within past 30 days or 5-half lives of investigational product, whichever is longer; * have received an investigational intervention for sars-cov-2 prophylaxis within 30 days before dosing; * pregnant or lactating women; * anticipated hospitalization or transfer to another medical site which is not a study site within 72 hours; * participants unable to follow the protocol during the study; * participants deemed inappropriate for enrollment by the investigator due to other factors.

* have known allergies to any of the components used in the formulation of the scta01/placebo; * participants with a history of severe anaphylaxis, such as severe anaphylactic reaction, urticaria, and angioedema; * have spo2 ≤ 93% on room air at sea level or pao2/fio2 \< 300, respiratory rate ≥30 per minute, heart rate ≥125 per minute (fda); * require mechanical ventilation or anticipated impending need for mechanical ventilation; * suspected or proven serious bacterial, fungal, viral, or other infection (besides covid-19) that in the opinion of the investigator could constitute a risk when taking part in this study; * have any serious concomitant systemic disease, condition or disorder that, in the opinion of the investigator, should preclude participation in this study; * have any co-morbidity requiring surgery within \<29 days, or that is considered life threatening within 29 days; * have a history of previous sars-cov-2 infection; * received convalescent plasma, covid-19 vaccine, or anti-sars-cov-2 spike(s) protein targeted therapy; * have participated in a clinical study involving an investigational intervention within past 30 days or 5-half lives of investigational product, whichever is longer; * have received an investigational intervention for sars-cov-2 prophylaxis within 30 days before dosing; * pregnant or lactating women; * anticipated hospitalization or transfer to another medical site which is not a study site within 72 hours; * participants unable to follow the protocol during the study; * participants deemed inappropriate for enrollment by the investigator due to other factors.

- have known allergies to any of the components used in the formulation of the scta01/placebo; - participants with a history of severe anaphylaxis, such as severe anaphylactic reaction, urticaria, and angioedema; - have spo2 ≤ 93% on room air at sea level or pao2/fio2 < 300, respiratory rate ≥30 per minute, heart rate ≥125 per minute (fda); - require mechanical ventilation or anticipated impending need for mechanical ventilation; - suspected or proven serious bacterial, fungal, viral, or other infection (besides covid-19) that in the opinion of the investigator could constitute a risk when taking part in this study; - have any serious concomitant systemic disease, condition or disorder that, in the opinion of the investigator, should preclude participation in this study; - have any co-morbidity requiring surgery within <29 days, or that is considered life threatening within 29 days; - have a history of previous sars-cov-2 infection; - received convalescent plasma, covid-19 vaccine, or anti-sars-cov-2 spike(s) protein targeted therapy; - have participated in a clinical study involving an investigational intervention within past 30 days or 5-half lives of investigational product, whichever is longer; - have received an investigational intervention for sars-cov-2 prophylaxis within 30 days before dosing; - pregnant or lactating women; - anticipated hospitalization or transfer to another medical site which is not a study site within 72 hours; - participants unable to follow the protocol during the study; - participants deemed inappropriate for enrollment by the investigator due to other factors.

- have known allergies to any of the components used in the formulation of the scta01/placebo; - participants with a history of severe anaphylaxis, such as severe anaphylactic reaction, urticaria, and angioedema; - have spo2 ≤ 93% on room air at sea level or pao2/fio2 < 300, respiratory rate ≥30 per minute, heart rate ≥125 per minute (fda); - require mechanical ventilation or anticipated impending need for mechanical ventilation; - suspected or proven serious bacterial, fungal, viral, or other infection (besides covid-19) that in the opinion of the investigator could constitute a risk when taking part in this study; - have any serious concomitant systemic disease, condition or disorder that, in the opinion of the investigator, should preclude participation in this study; - have any co-morbidity requiring surgery within <29 days, or that is considered life threatening within 29 days; - have a history of previous sars-cov-2 infection; - received convalescent plasma, covid-19 vaccine, or anti-sars-cov-2 spike(s) protein targeted therapy; - have participated in a clinical study involving an investigational intervention within past 30 days or 5-half lives of investigational product, whichever is longer; - have received an investigational intervention for sars-cov-2 prophylaxis within 30 days before dosing; - pregnant or lactating women; - anticipated hospitalization or transfer to another medical site which is not a study site within 72 hours; - participants unable to follow the protocol during the study; - participants deemed inappropriate for enrollment by the investigator due to other factors.