Inclusion criteria:  Participant must be 32 weeks estimated gestational age (EGA), day of life (DOL) 0 to <18 years of age inclusive, at either the time of participant's signed assent (if age-appropriate) or parent(s)/legally authorized representative signing the informed consent. Participants with mild-moderate COVID-19. Participants at risk of disease progression with at least one of the following criteria: Age <1 year; Diabetes mellitus; Genetic or metabolic diseases; Obesity ); Cardiovascular disease; Sickle cell disease; Pulmonary disease; Neurologic disease; Immunosuppressed ; Baseline medical complexity (gastrostomy- or jejunostomy-dependence, parenteral nutrition dependence, tracheostomy-dependence, Baseline oxygen requirement, use of Continuous positive airway pressure [CPAP]/ Bilevel positive airway pressure [BiPAP]/ventilator support).  Exclusion Criteria  Participant is pregnant or breastfeeding. Participant is currently hospitalized, or judged by the investigator as likely to require hospitalization in the next 24 hours, due to severe or critical COVID-19. Multisystem inflammatory syndrome in children (MIS-C). Prior, current, or planned future use of any of the following treatments during the study period: COVID-19 convalescent plasma, Monoclonal antibodies (mAbs) against Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) (for example [e.g.], casirivimab/imdevimab), intravenous immunoglobulin (IVIG) for any indication, or dexamethasone specifically for treatment of COVID-19. Current use of COVID-19 treatment (authorized, approved, or investigational).  The following exclusions related to use of an authorized or approved vaccine for SARS-CoV-2 are applicable:  Receipt of any authorized or approved vaccine for SARS-CoV-2 within 48 hours prior to dosing. Planned use of any authorized or approved vaccine for SARS-CoV-2 within 90 days of study drug administration per current Centers for Disease Control and Prevention (CDC) recommendations. Receipt of any non-SARS-CoV-2 vaccines within 14 days (for non-live vaccines) or 28 days (for live vaccine) of screening. Currently enrolled in another clinical study. Infants <24 weeks of age: maternal receipt of IVIG, SARS-CoV-2-directed convalescent plasma or SARS-CoV-2-directed mAb(s) within 3 months prior to birth or within 5 half-lives of the investigational product (whichever is longer).