inclusion criteria: - subjects must be 18 years of age or older - recent close contact with a person with covid-19, i.e. last close contact occurred within 7 days of anticipated infusion of study product. it is anticipated that most contacts will be household contacts with extensive interaction. all must meet the cdc criteria for close contacts. this includes healthcare workers at higher risk of developing severe disease. or - recent self-reported or documented evidence of infection by nasal swab pcr that is positive for sars-cov-2, i.e., nasal sample was collected within 7 days or 10 days of anticipated infusion of study product for those who are asymptomatic or symptomatic, respectively. - evidence of infection by nasal swab pcr that is positive for sars-cov-2 at screening visit. - may or may not be hospitalized. - no symptoms or no more than 5 days of mild symptoms at the time of screening. mild symptoms (rated by participant as mild and not interfering with normal daily activities) may include: - mild rhinorrhea - mild sore throat or throat irritation - mild nonproductive cough - mild fatigue (able to perform activities of daily living (adls)) - risk for severe covid-19 based on a risk score of ≥ 1 calculated risk score of ≥ 1 point, with risk factors based on center for disease control and prevention (cdc) description - age 65-74: 1 point - age ≥ 75: 2 points - known cardiovascular disease (including hypertension): 1 point - diabetes mellitus: 1 point - pulmonary disease (copd, moderate to severe asthma, current smoking or other): 1 point - morbid obesity: 1 point - immunocompromised state: 1 point received a bone marrow or solid organ transplant at any time, received chemotherapy for a malignancy within the past 6 months, has an acquired or congenital immunodeficiency, currently receiving immunosuppressive or immune modulating medications, hiv with non-suppressed viral load and/or cluster of differentiation 4 (cd4+) t cell count <200 cells/ml).

inclusion criteria: - subjects must be 18 years of age or older - recent close contact with a person with covid-19, i.e. last close contact occurred within 7 days of anticipated infusion of study product. it is anticipated that most contacts will be household contacts with extensive interaction. all must meet the cdc criteria for close contacts. this includes healthcare workers at higher risk of developing severe disease. or - recent self-reported or documented evidence of infection by nasal swab pcr that is positive for sars-cov-2, i.e., nasal sample was collected within 7 days or 10 days of anticipated infusion of study product for those who are asymptomatic or symptomatic, respectively. - evidence of infection by nasal swab pcr that is positive for sars-cov-2 at screening visit. - may or may not be hospitalized. - no symptoms or no more than 5 days of mild symptoms at the time of screening. mild symptoms (rated by participant as mild and not interfering with normal daily activities) may include: - mild rhinorrhea - mild sore throat or throat irritation - mild nonproductive cough - mild fatigue (able to perform activities of daily living (adls)) - risk for severe covid-19 based on a risk score of ≥ 1 calculated risk score of ≥ 1 point, with risk factors based on center for disease control and prevention (cdc) description - age 65-74: 1 point - age ≥ 75: 2 points - known cardiovascular disease (including hypertension): 1 point - diabetes mellitus: 1 point - pulmonary disease (copd, moderate to severe asthma, current smoking or other): 1 point - morbid obesity: 1 point - immunocompromised state: 1 point received a bone marrow or solid organ transplant at any time, received chemotherapy for a malignancy within the past 6 months, has an acquired or congenital immunodeficiency, currently receiving immunosuppressive or immune modulating medications, hiv with non-suppressed viral load and/or cluster of differentiation 4 (cd4+) t cell count <200 cells/ml).

inclusion criteria: group b: sars-cov-2 pcr positive but asymptomatic or mild symptoms at screening - subjects must be 18 years of age or older - close contact* of a person with covid-19 within the last 7 days. it is anticipated that most contacts will be household contacts with extensive interaction. all must meet the cdc criteria for close contacts. - evidence of infection by nasopharyngeal swab pcr that is positive for sars-cov-2 - no symptoms or no more than 5 days of mild symptoms at the time of screening. mild symptoms+ may include: - mild rhinorrhea - mild sore throat or throat irritation - mild nonproductive cough - mild fatigue (able to perform activities of daily living (adls)) - high risk for severe covid-19 based on a risk score of ≥ 2 calculated risk score of ≥ 2 points, with risk factors based on center for disease control and prevention (cdc) description - age 65-74: 1 point - age ≥ 75: 2 points - known cardiovascular disease (including hypertension): 1 point - diabetes mellitus: 1 point - pulmonary disease (copd, moderate to severe asthma, current smoking or other): 1 point - morbid obesity: 1 point - immunocompromised state: 1 point received a bone marrow or solid organ transplant at any time, received chemotherapy for a malignancy within the past 6 months, has an acquired or congenital immunodeficiency, currently receiving immunosuppressive or immune modulating medications, hiv with non-suppressed viral load and/or cluster of differentiation 4 (cd4+) t cell count <200 cells/ml). - mild symptoms are rated by participant as mild and not interfering with normal daily activities group c: sars-cov-2 pcr negative (uninfected) at time of screening but asymptomatic or mildly symptomatic at screening - subjects must be 18 years of age or older - close contact* of a person with covid-19 within the last 7 days. it is anticipated that most contacts will be household contacts with extensive interaction. all must meet the cdc criteria for close contacts. - nasopharyngeal swab negative for sars-cov-2 at screening - no symptoms or no more than 5 days of mild symptoms at the time of screening. mild symptoms+ may include: - mild rhinorrhea - mild sore throat or throat irritation - mild nonproductive cough - mild fatigue (able to perform adls) - high risk for severe covid-19 based on a risk score of ≥ 2, as above.* - close contact is defined by cdc as being within approximately 6 feet (2 meters) of a covid-19 case for a prolonged period of time (without ppe); close contact can occur while caring for, living with, visiting, or sharing a healthcare waiting area or room with a covid-19 case. - mild symptoms are rated by participant as mild and not interfering with normal daily activities

inclusion criteria: group b: sars-cov-2 pcr positive but asymptomatic or mild symptoms at screening - subjects must be 18 years of age or older - close contact* of a person with covid-19 within the last 7 days. it is anticipated that most contacts will be household contacts with extensive interaction. all must meet the cdc criteria for close contacts. - evidence of infection by nasopharyngeal swab pcr that is positive for sars-cov-2 - no symptoms or no more than 5 days of mild symptoms at the time of screening. mild symptoms+ may include: - mild rhinorrhea - mild sore throat or throat irritation - mild nonproductive cough - mild fatigue (able to perform activities of daily living (adls)) - high risk for severe covid-19 based on a risk score of ≥ 2 calculated risk score of ≥ 2 points, with risk factors based on center for disease control and prevention (cdc) description - age 65-74: 1 point - age ≥ 75: 2 points - known cardiovascular disease (including hypertension): 1 point - diabetes mellitus: 1 point - pulmonary disease (copd, moderate to severe asthma, current smoking or other): 1 point - morbid obesity: 1 point - immunocompromised state: 1 point received a bone marrow or solid organ transplant at any time, received chemotherapy for a malignancy within the past 6 months, has an acquired or congenital immunodeficiency, currently receiving immunosuppressive or immune modulating medications, hiv with non-suppressed viral load and/or cluster of differentiation 4 (cd4+) t cell count <200 cells/ml). - mild symptoms are rated by participant as mild and not interfering with normal daily activities group c: sars-cov-2 pcr negative (uninfected) at time of screening but asymptomatic or mildly symptomatic at screening - subjects must be 18 years of age or older - close contact* of a person with covid-19 within the last 7 days. it is anticipated that most contacts will be household contacts with extensive interaction. all must meet the cdc criteria for close contacts. - nasopharyngeal swab negative for sars-cov-2 at screening - no symptoms or no more than 5 days of mild symptoms at the time of screening. mild symptoms+ may include: - mild rhinorrhea - mild sore throat or throat irritation - mild nonproductive cough - mild fatigue (able to perform adls) - high risk for severe covid-19 based on a risk score of ≥ 2, as above.* - close contact is defined by cdc as being within approximately 6 feet (2 meters) of a covid-19 case for a prolonged period of time (without ppe); close contact can occur while caring for, living with, visiting, or sharing a healthcare waiting area or room with a covid-19 case. - mild symptoms are rated by participant as mild and not interfering with normal daily activities