* women who are pregnant, lactating, or of childbearing potential and not using a highly effective method of contraception or abstinence from at least 4 weeks prior to study intervention administration and until at least 6 months after study intervention administration. * known hypersensitivity to any component of the study intervention. * previous hypersensitivity or severe adverse reaction following administration of a mab. * acute (time-limited) or febrile (temperature ≥ 38.0°c \[100.4ºf\]) illness/infection on day prior to or day of planned dosing; participants excluded for transient acute illness may be dosed if illness resolves within the screening period or may be rescreened once. * blood drawn in excess of a total of 450 ml (1 unit) for any reason within 30 days prior to visit 1. * clinically significant bleeding disorder (eg, factor deficiency, coagulopathy, or platelet disorder), or prior history of significant bleeding or bruising following im injections or venipuncture. * receipt of immunoglobulin (non-covid related) or blood products within 6 months prior to visit 1. * previous receipt of a mab against sars-cov-2. * receipt of a covid-19 vaccine within 3 months prior to visit 1. * receipt of a covid-19 antiviral for prophylaxis within 3 months prior to visit 1 * covid-19 within 3 months prior to visit 1 (confirmed either by laboratory testing or a rapid test \[including at home testing\]). * receipt of any imp in the preceding 90 days or expected receipt of imp during the period of study follow-up, or concurrent participation in another interventional study. * known or suspected congenital or acquired immunodeficiency, or receipt of immunosuppressive therapy, including any course of glucocorticoid therapy exceeding 2 weeks of prednisone or equivalent at a dose of 20 mg daily or every other day within 6 months prior to screening. * active infection with hepatitis b or c. * serum creatinine, ast, or alt above 1.5 × uln at screening * history of malignancy other than treated non-melanoma skin cancers or locally-treated cervical cancer in previous 5 years. parent study - main cohort participants (phase iii): parent study - main cohort inclusion criteria: * participant must be 12 years of age or older at the time of signing the informed consent. * negative rapid antigen test prior to dosing at visit 1. * weight ≥ 40 kg at screening. * participants must satisfy at least 1 of the following risk factors at enrollment: * have solid tumor cancer and be on active immunosuppressive treatment * have hematologic malignancy * transplant participants must satisfy at least one of the following: 1. have had a solid organ transplant within 2 years and / or 2. had a hematopoietic stem cell transplant within 2 years and / or 3. who have chronic graft-versus-host disease 4. participants who previously had a solid organ transplant or hematopoietic stem cell transplant more than 2 years prior to visit 1 may also be eligible based on the inclusion criterion for immunosuppressive treatment * are actively taking immunosuppressive medicines (eg, are using corticosteroids \[ie, ≥ 20 mg prednisone or equivalent per day when administered for ≥ 2 weeks\], high dose alkylating agents, antimetabolites, transplant-related immunosuppressive drugs, cancer chemotherapeutic agents classified as severely immunosuppressive \[eg, bruton's tyrosine kinase inhibitors\], tumor-necrosis blockers, or other immunosuppressive or immunomodulatory biologic agents (eg, for rheumatic diseases) * received chimeric antigen receptor t cell therapy * within 1 year of receiving b-cell depleting therapies (eg, rituximab, ocrelizumab, ofatumumab, alemtuzumab) * have a moderate or severe primary (eg, digeorge syndrome) or secondary (eg, hemodialysis) immunodeficiency * advanced or untreated hiv infection (people with hiv and cd4 cell counts \< 200/mm3 within 6 months of visit 1, history of an aids-defining illness without immune reconstitution, or clinical manifestations of symptomatic hiv) * medically stable defined as disease not requiring significant change in maintenance therapy or hospitalization for worsening disease or any recent cv event (eg, acute myocardial infarction, thromboembolic event) during the 1 month prior to enrollment, with no acute change in condition at the time of study enrollment as judged by the investigator and no expected changes at the time of the enrollment. * able to understand and comply with all study requirements/procedures (if applicable, with assistance by caregiver, surrogate, or legally authorized representative or equivalent representative as locally defined), including those at illness visits, based on the assessment of the investigator. parent study - main cohort

* women who are pregnant, lactating, or of childbearing potential and not using a highly effective method of contraception or abstinence from at least 4 weeks prior to study intervention administration and until at least 6 months after study intervention administration. * known hypersensitivity to any component of the study intervention. * previous hypersensitivity or severe adverse reaction following administration of a mab. * acute (time-limited) or febrile (temperature ≥ 38.0°c \[100.4ºf\]) illness/infection on day prior to or day of planned dosing; participants excluded for transient acute illness may be dosed if illness resolves within the screening period or may be rescreened once. * blood drawn in excess of a total of 450 ml (1 unit) for any reason within 30 days prior to visit 1. * clinically significant bleeding disorder (eg, factor deficiency, coagulopathy, or platelet disorder), or prior history of significant bleeding or bruising following im injections or venipuncture. * receipt of immunoglobulin (non-covid related) or blood products within 6 months prior to visit 1. * previous receipt of a mab against sars-cov-2. * receipt of a covid-19 vaccine within 3 months prior to visit 1. * receipt of a covid-19 antiviral for prophylaxis within 3 months prior to visit 1 * covid-19 within 3 months prior to visit 1 (confirmed either by laboratory testing or a rapid test \[including at home testing\]). * receipt of any imp in the preceding 90 days or expected receipt of imp during the period of study follow-up, or concurrent participation in another interventional study. * known or suspected congenital or acquired immunodeficiency, or receipt of immunosuppressive therapy, including any course of glucocorticoid therapy exceeding 2 weeks of prednisone or equivalent at a dose of 20 mg daily or every other day within 6 months prior to screening. * active infection with hepatitis b or c. * serum creatinine, ast, or alt above 1.5 × uln at screening * history of malignancy other than treated non-melanoma skin cancers or locally-treated cervical cancer in previous 5 years. parent study - main cohort participants (phase iii): parent study - main cohort inclusion criteria: * participant must be 12 years of age or older at the time of signing the informed consent. * negative rapid antigen test prior to dosing at visit 1. * weight ≥ 40 kg at screening. * participants must satisfy at least 1 of the following risk factors at enrollment: * have solid tumor cancer and be on active immunosuppressive treatment * have hematologic malignancy * transplant participants must satisfy at least one of the following: 1. have had a solid organ transplant within 2 years and / or 2. had a hematopoietic stem cell transplant within 2 years and / or 3. who have chronic graft-versus-host disease 4. participants who previously had a solid organ transplant or hematopoietic stem cell transplant more than 2 years prior to visit 1 may also be eligible based on the inclusion criterion for immunosuppressive treatment * are actively taking immunosuppressive medicines (eg, are using corticosteroids \[ie, ≥ 20 mg prednisone or equivalent per day when administered for ≥ 2 weeks\], high dose alkylating agents, antimetabolites, transplant-related immunosuppressive drugs, cancer chemotherapeutic agents classified as severely immunosuppressive \[eg, bruton's tyrosine kinase inhibitors\], tumor-necrosis blockers, or other immunosuppressive or immunomodulatory biologic agents (eg, for rheumatic diseases) * received chimeric antigen receptor t cell therapy * within 1 year of receiving b-cell depleting therapies (eg, rituximab, ocrelizumab, ofatumumab, alemtuzumab) * have a moderate or severe primary (eg, digeorge syndrome) or secondary (eg, hemodialysis) immunodeficiency * advanced or untreated hiv infection (people with hiv and cd4 cell counts \< 200/mm3 within 6 months of visit 1, history of an aids-defining illness without immune reconstitution, or clinical manifestations of symptomatic hiv) * medically stable defined as disease not requiring significant change in maintenance therapy or hospitalization for worsening disease or any recent cv event (eg, acute myocardial infarction, thromboembolic event) during the 1 month prior to enrollment, with no acute change in condition at the time of study enrollment as judged by the investigator and no expected changes at the time of the enrollment. * able to understand and comply with all study requirements/procedures (if applicable, with assistance by caregiver, surrogate, or legally authorized representative or equivalent representative as locally defined), including those at illness visits, based on the assessment of the investigator. parent study - main cohort

women who are pregnant, lactating, or of childbearing potential and not using a highly effective method of contraception or abstinence from at least 4 weeks prior to study intervention administration and until at least 6 months after study intervention administration. known hypersensitivity to any component of the study intervention. previous hypersensitivity or severe adverse reaction following administration of a mab. acute (time-limited) or febrile (temperature ≥ 38.0°c [100.4ºf]) illness/infection on day prior to or day of planned dosing; participants excluded for transient acute illness may be dosed if illness resolves within the screening period or may be rescreened once. blood drawn in excess of a total of 450 ml (1 unit) for any reason within 30 days prior to visit 1. clinically significant bleeding disorder (eg, factor deficiency, coagulopathy, or platelet disorder), or prior history of significant bleeding or bruising following im injections or venipuncture. receipt of immunoglobulin (non-covid related) or blood products within 6 months prior to visit 1. previous receipt of a mab against sars-cov-2. receipt of a covid-19 vaccine within 3 months prior to visit 1. receipt of a covid-19 antiviral for prophylaxis within 3 months prior to visit 1 covid-19 within 3 months prior to visit 1 (confirmed either by laboratory testing or a rapid test [including at home testing]). receipt of any imp in the preceding 90 days or expected receipt of imp during the period of study follow-up, or concurrent participation in another interventional study. known or suspected congenital or acquired immunodeficiency, or receipt of immunosuppressive therapy, including any course of glucocorticoid therapy exceeding 2 weeks of prednisone or equivalent at a dose of 20 mg daily or every other day within 6 months prior to screening. active infection with hepatitis b or c. serum creatinine, ast, or alt above 1.5 × uln at screening history of malignancy other than treated non-melanoma skin cancers or locally-treated cervical cancer in previous 5 years. parent study - main cohort participants (phase iii): parent study - main cohort inclusion criteria: participant must be 12 years of age or older at the time of signing the informed consent. negative rapid antigen test prior to dosing at visit 1. weight ≥ 40 kg at screening. participants must satisfy at least 1 of the following risk factors at enrollment: have solid tumor cancer and be on active immunosuppressive treatment have hematologic malignancy transplant participants must satisfy at least one of the following: have had a solid organ transplant within 2 years and / or had a hematopoietic stem cell transplant within 2 years and / or who have chronic graft-versus-host disease participants who previously had a solid organ transplant or hematopoietic stem cell transplant more than 2 years prior to visit 1 may also be eligible based on the inclusion criterion for immunosuppressive treatment are actively taking immunosuppressive medicines (eg, are using corticosteroids [ie, ≥ 20 mg prednisone or equivalent per day when administered for ≥ 2 weeks], high dose alkylating agents, antimetabolites, transplant-related immunosuppressive drugs, cancer chemotherapeutic agents classified as severely immunosuppressive [eg, bruton's tyrosine kinase inhibitors], tumor-necrosis blockers, or other immunosuppressive or immunomodulatory biologic agents (eg, for rheumatic diseases) received chimeric antigen receptor t cell therapy within 1 year of receiving b-cell depleting therapies (eg, rituximab, ocrelizumab, ofatumumab, alemtuzumab) have a moderate or severe primary (eg, digeorge syndrome) or secondary (eg, hemodialysis) immunodeficiency advanced or untreated hiv infection (people with hiv and cd4 cell counts < 200/mm3 within 6 months of visit 1, history of an aids-defining illness without immune reconstitution, or clinical manifestations of symptomatic hiv) medically stable defined as disease not requiring significant change in maintenance therapy or hospitalization for worsening disease or any recent cv event (eg, acute myocardial infarction, thromboembolic event) during the 1 month prior to enrollment, with no acute change in condition at the time of study enrollment as judged by the investigator and no expected changes at the time of the enrollment. able to understand and comply with all study requirements/procedures (if applicable, with assistance by caregiver, surrogate, or legally authorized representative or equivalent representative as locally defined), including those at illness visits, based on the assessment of the investigator. parent study - main cohort

women who are pregnant, lactating, or of childbearing potential and not using a highly effective method of contraception or abstinence from at least 4 weeks prior to study intervention administration and until at least 6 months after study intervention administration. known hypersensitivity to any component of the study intervention. previous hypersensitivity or severe adverse reaction following administration of a mab. acute (time-limited) or febrile (temperature ≥ 38.0°c [100.4ºf]) illness/infection on day prior to or day of planned dosing; participants excluded for transient acute illness may be dosed if illness resolves within the screening period or may be rescreened once. blood drawn in excess of a total of 450 ml (1 unit) for any reason within 30 days prior to visit 1. clinically significant bleeding disorder (eg, factor deficiency, coagulopathy, or platelet disorder), or prior history of significant bleeding or bruising following im injections or venipuncture. receipt of immunoglobulin (non-covid related) or blood products within 6 months prior to visit 1. previous receipt of a mab against sars-cov-2. receipt of a covid-19 vaccine within 3 months prior to visit 1. receipt of a covid-19 antiviral for prophylaxis within 3 months prior to visit 1 covid-19 within 3 months prior to visit 1 (confirmed either by laboratory testing or a rapid test [including at home testing]). receipt of any imp in the preceding 90 days or expected receipt of imp during the period of study follow-up, or concurrent participation in another interventional study. known or suspected congenital or acquired immunodeficiency, or receipt of immunosuppressive therapy, including any course of glucocorticoid therapy exceeding 2 weeks of prednisone or equivalent at a dose of 20 mg daily or every other day within 6 months prior to screening. active infection with hepatitis b or c. serum creatinine, ast, or alt above 1.5 × uln at screening history of malignancy other than treated non-melanoma skin cancers or locally-treated cervical cancer in previous 5 years. parent study - main cohort participants (phase iii): parent study - main cohort inclusion criteria: participant must be 12 years of age or older at the time of signing the informed consent. negative rapid antigen test prior to dosing at visit 1. weight ≥ 40 kg at screening. participants must satisfy at least 1 of the following risk factors at enrollment: have solid tumor cancer and be on active immunosuppressive treatment have hematologic malignancy transplant participants must satisfy at least one of the following: have had a solid organ transplant within 2 years and / or had a hematopoietic stem cell transplant within 2 years and / or who have chronic graft-versus-host disease participants who previously had a solid organ transplant or hematopoietic stem cell transplant more than 2 years prior to visit 1 may also be eligible based on the inclusion criterion for immunosuppressive treatment are actively taking immunosuppressive medicines (eg, are using corticosteroids [ie, ≥ 20 mg prednisone or equivalent per day when administered for ≥ 2 weeks], high dose alkylating agents, antimetabolites, transplant-related immunosuppressive drugs, cancer chemotherapeutic agents classified as severely immunosuppressive [eg, bruton's tyrosine kinase inhibitors], tumor-necrosis blockers, or other immunosuppressive or immunomodulatory biologic agents (eg, for rheumatic diseases) received chimeric antigen receptor t cell therapy within 1 year of receiving b-cell depleting therapies (eg, rituximab, ocrelizumab, ofatumumab, alemtuzumab) have a moderate or severe primary (eg, digeorge syndrome) or secondary (eg, hemodialysis) immunodeficiency advanced or untreated hiv infection (people with hiv and cd4 cell counts < 200/mm3 within 6 months of visit 1, history of an aids-defining illness without immune reconstitution, or clinical manifestations of symptomatic hiv) medically stable defined as disease not requiring significant change in maintenance therapy or hospitalization for worsening disease or any recent cv event (eg, acute myocardial infarction, thromboembolic event) during the 1 month prior to enrollment, with no acute change in condition at the time of study enrollment as judged by the investigator and no expected changes at the time of the enrollment. able to understand and comply with all study requirements/procedures (if applicable, with assistance by caregiver, surrogate, or legally authorized representative or equivalent representative as locally defined), including those at illness visits, based on the assessment of the investigator. parent study - main cohort

women who are pregnant, lactating, or of childbearing potential and not using a highly effective method of contraception or abstinence from at least 4 weeks prior to study intervention administration and until at least 6 months after study intervention administration. known hypersensitivity to any component of the study intervention. previous hypersensitivity or severe adverse reaction following administration of a mab. acute (time-limited) or febrile (temperature ≥ 38.0°c [100.4ºf]) illness/infection on day prior to or day of planned dosing; participants excluded for transient acute illness may be dosed if illness resolves within the screening period or may be rescreened once. blood drawn in excess of a total of 450 ml (1 unit) for any reason within 30 days prior to visit 1. clinically significant bleeding disorder (eg, factor deficiency, coagulopathy, or platelet disorder), or prior history of significant bleeding or bruising following im injections or venipuncture. receipt of immunoglobulin (non-covid related) or blood products within 6 months prior to visit 1. previous receipt of a mab against sars-cov-2. receipt of a covid-19 vaccine within 3 months prior to visit 1. receipt of a covid-19 antiviral for prophylaxis within 3 months prior to visit 1 covid-19 within 3 months prior to visit 1 (confirmed either by laboratory testing or a rapid test [including at home testing]). receipt of any imp in the preceding 90 days or expected receipt of imp during the period of study follow-up, or concurrent participation in another interventional study. known or suspected congenital or acquired immunodeficiency, or receipt of immunosuppressive therapy, including any course of glucocorticoid therapy exceeding 2 weeks of prednisone or equivalent at a dose of 20 mg daily or every other day within 6 months prior to screening. active infection with hepatitis b or c. serum creatinine, ast, or alt above 1.5 × uln at screening history of malignancy other than treated non-melanoma skin cancers or locally-treated cervical cancer in previous 5 years. parent study - main cohort participants (phase iii): parent study - main cohort inclusion criteria: participant must be 12 years of age or older at the time of signing the informed consent. negative rapid antigen test prior to dosing at visit 1. weight ≥ 40 kg at screening. participants must satisfy at least 1 of the following risk factors at enrollment: have solid tumor cancer and be on active immunosuppressive treatment have hematologic malignancy transplant participants must satisfy at least one of the following: have had a solid organ transplant within 2 years and / or had a hematopoietic stem cell transplant within 2 years and / or who have chronic graft-versus-host disease participants who previously had a solid organ transplant or hematopoietic stem cell transplant more than 2 years prior to visit 1 may also be eligible based on the inclusion criterion for immunosuppressive treatment are actively taking immunosuppressive medicines (eg, are using corticosteroids [ie, ≥ 20 mg prednisone or equivalent per day when administered for ≥ 2 weeks], high dose alkylating agents, antimetabolites, transplant-related immunosuppressive drugs, cancer chemotherapeutic agents classified as severely immunosuppressive [eg, bruton's tyrosine kinase inhibitors], tumor-necrosis blockers, or other immunosuppressive or immunomodulatory biologic agents (eg, for rheumatic diseases) received chimeric antigen receptor t cell therapy within 1 year of receiving b-cell depleting therapies (eg, rituximab, ocrelizumab, ofatumumab, alemtuzumab) have a moderate or severe primary (eg, digeorge syndrome) or secondary (eg, hemodialysis) immunodeficiency advanced or untreated hiv infection (people with hiv and cd4 cell counts < 200/mm3 within 6 months of visit 1, history of an aids-defining illness without immune reconstitution, or clinical manifestations of symptomatic hiv) medically stable defined as disease not requiring significant change in maintenance therapy or hospitalization for worsening disease or any recent cardiovascular event (eg, acute myocardial infarction, thromboembolic event) during the 1 month prior to enrollment, with no acute change in condition at the time of study enrollment as judged by the investigator and no expected changes at the time of the enrollment. able to understand and comply with all study requirements/procedures (if applicable, with assistance by caregiver, surrogate, or legally authorized representative or equivalent representative as locally defined), including those at illness visits, based on the assessment of the investigator. parent study - main cohort

women who are pregnant, lactating, or of childbearing potential and not using a highly effective method of contraception or abstinence from at least 4 weeks prior to study intervention administration and until at least 6 months after study intervention administration. known hypersensitivity to any component of the study intervention. previous hypersensitivity or severe adverse reaction following administration of a mab. acute (time-limited) or febrile (temperature ≥ 38.0°c [100.4ºf]) illness/infection on day prior to or day of planned dosing; participants excluded for transient acute illness may be dosed if illness resolves within the screening period or may be rescreened once. blood drawn in excess of a total of 450 ml (1 unit) for any reason within 30 days prior to visit 1. clinically significant bleeding disorder (eg, factor deficiency, coagulopathy, or platelet disorder), or prior history of significant bleeding or bruising following im injections or venipuncture. receipt of immunoglobulin (non-covid related) or blood products within 6 months prior to visit 1. previous receipt of a mab against sars-cov-2. receipt of a covid-19 vaccine within 3 months prior to visit 1. receipt of a covid-19 antiviral for prophylaxis within 3 months prior to visit 1 covid-19 within 3 months prior to visit 1 (confirmed either by laboratory testing or a rapid test [including at home testing]). receipt of any imp in the preceding 90 days or expected receipt of imp during the period of study follow-up, or concurrent participation in another interventional study. known or suspected congenital or acquired immunodeficiency, or receipt of immunosuppressive therapy, including any course of glucocorticoid therapy exceeding 2 weeks of prednisone or equivalent at a dose of 20 mg daily or every other day within 6 months prior to screening. active infection with hepatitis b or c. serum creatinine, ast, or alt above 1.5 × uln at screening history of malignancy other than treated non-melanoma skin cancers or locally-treated cervical cancer in previous 5 years. parent study - main cohort participants (phase iii): parent study - main cohort inclusion criteria: participant must be 12 years of age or older at the time of signing the informed consent. negative rapid antigen test prior to dosing at visit 1. weight ≥ 40 kg at screening. participants must satisfy at least 1 of the following risk factors at enrollment: have solid tumor cancer and be on active immunosuppressive treatment have hematologic malignancy transplant participants must satisfy at least one of the following: have had a solid organ transplant within 2 years and / or had a hematopoietic stem cell transplant within 2 years and / or who have chronic graft-versus-host disease participants who previously had a solid organ transplant or hematopoietic stem cell transplant more than 2 years prior to visit 1 may also be eligible based on the inclusion criterion for immunosuppressive treatment are actively taking immunosuppressive medicines (eg, are using corticosteroids [ie, ≥ 20 mg prednisone or equivalent per day when administered for ≥ 2 weeks], high dose alkylating agents, antimetabolites, transplant-related immunosuppressive drugs, cancer chemotherapeutic agents classified as severely immunosuppressive [eg, bruton's tyrosine kinase inhibitors], tumor-necrosis blockers, or other immunosuppressive or immunomodulatory biologic agents (eg, for rheumatic diseases) received chimeric antigen receptor t cell therapy within 1 year of receiving b-cell depleting therapies (eg, rituximab, ocrelizumab, ofatumumab, alemtuzumab) have a moderate or severe primary (eg, digeorge syndrome) or secondary (eg, hemodialysis) immunodeficiency advanced or untreated hiv infection (people with hiv and cd4 cell counts < 200/mm3 within 6 months of visit 1, history of an aids-defining illness without immune reconstitution, or clinical manifestations of symptomatic hiv) medically stable defined as disease not requiring significant change in maintenance therapy or hospitalization for worsening disease or any recent cardiovascular event (eg, acute myocardial infarction, thromboembolic event) during the 1 month prior to enrollment, with no acute change in condition at the time of study enrollment as judged by the investigator and no expected changes at the time of the enrollment. able to understand and comply with all study requirements/procedures (if applicable, with assistance by caregiver, surrogate, or legally authorized representative or equivalent representative as locally defined), including those at illness visits, based on the assessment of the investigator. parent study - main cohort

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