Key Inclusion Criteria:  Is <12 years of age and ≥3 kg to <40 kg at the time parental/guardian consent is signed  Has at least one risk factor for developing severe COVID-19 if they were to become infected, such as:  Obesity (BMI [kg/m2] ≥95th percentile for age and sex based on CDC growth charts) Cardiovascular disease Chronic lung disease Type 1 or type 2 diabetes mellitus Chronic kidney disease, including those on dialysis Chronic liver disease Immunocompromised or immunodeficient, based on Investigator's assessment (examples include cancer treatment, bone marrow or organ transplantation, immune deficiencies, HIV infection, sickle cell anemia, thalassemia, and prolonged use of immune-weakening medications) Medical complexities (examples include any underlying genetic condition, neurologic condition, metabolic condition, or congenital heart disease) Any other condition deemed by the Investigator to be a risk factor for severe COVID-19  Key Exclusion Criteria:  Has positive diagnostic test for SARS-CoV-2 infection from a sample collected during screening ≤7 days prior to study drug administration Note: The sample for the test should be collected ≤7 days within study drug administration, and the result should be reviewed and confirmed negative prior to dosing. Historical records will not be accepted. Has active respiratory or non-respiratory symptoms consistent with COVID-19 in the opinion of the Investigator Has subject-reported clinical history of COVID-19, as determined by Investigator, within the last 90 days Has subject-reported history of prior Emergency Use Authorization (EUA)/approved positive diagnostic test for SARSCoV-2 infection within the last 90 days Is currently hospitalized or was hospitalized for >24 hours for any reason within 14 days of the screening visit Prior use (within 90 days prior to study drug administration) or current use of any investigational, authorized, or approved passive antibody for prophylaxis of SARS-CoV-2 infection, including convalescent plasma, convalescent sera, hyperimmune globulin, or other monoclonal antibodies (eg, bamlanivimab and etesevimab, sotrovimab) Has initiated vaccination for SARS-CoV-2 with an investigational or approved vaccine, but has not completed the vaccine schedule as recommended by the vaccine manufacturer. Plans to receive an investigational or approved SARS-CoV-2 vaccine within 90 days after study drug administration, or per the recommended time frame from the current Centers for Disease Control vaccination guidelines (CDC, 2021b)  NOTE: Other protocol-defined Inclusion/ Exclusion Criteria apply