• Participant must be aged ≥ 29 weeks gestational age (GA) to < 18 years of age. - Participant must weigh a minimum of 1.5 kg. COHORT 1 - Increased risk of severe COVID-19 because of immunocompromised state or one or more comorbid conditions that increase the risk of severe COVID-19. - Increased risk for SARS-CoV-2 infection. - Medically stable (disease not requiring significant change in therapy or hospitalization for worsening disease during the one month prior to enrollment). - A negative RT-PCR test collected ≤ 3 days prior to Day 1 or a negative rapid SARS-CoV-2 antigen test at screening. - No COVID-19 symptoms prior to enrollment within 10 days of dosing. - Increased risk for SARS-CoV-2 infection. COHORT 2 - Increased risk of severe COVID-19 because of immunocompromised state or one or more comorbid conditions that increase the risk of severe COVID-19. - Medically stable (disease not requiring significant change in therapy or hospitalization for worsening disease during the one month prior to enrollment). - A positive RT-PCR test collected ≤ 3 days prior to Day 1 or a positive rapid SARS-CoV-2 antigen test at screening. - Symptomatic participants must be dosed with IMP no more than 7 days from the self-reported date of first reported sign/symptom. - Oxygenation saturation of ≥ 92% obtained at rest within 24 hours prior to Day 1 unless the potential participant regularly receives chronic supplementary oxygen for an underlying lung condition. Note that Cohort 2 will only be included if the indication is progressed in adults. COHORT 3 - Participants hospitalized with COVID-19 with a time between onset of symptoms and dosing AZD7442 of ≤ 7 days. - A positive RT-PCR test collected ≤ 3 days before Day 1 or a positive rapid SARS-CoV-2 antigen test at screening. - Spontaneous blood Alanine Aminotransferase (ALT)/Aspartate Transaminase (AST) levels ≤ 5 times the ULN. - Glomerular Filtration Rate (GFR) ≥ 30 mL/min/1.73 m2. Participants will receive IM AZD7442 unless they meet any of the following criteria for IV administration: - The participant has severe COVID-19. - Contraindication of intramuscular (IM) dose due to thrombocytopenia, coagulation defects or any other condition that would compromise the absorption of AZD7442 or safety of the participant. - Physician considers IV the appropriate route.

All Cohorts - Cohort 1: Significant infection or other acute illnesses including fever on or the day prior to receiving AZD7442. - History of SARS-CoV-1 or Middle East Respiratory Syndrome Coronavirus (MERS-CoV). - Cohorts 1 and 2: Current need for immediate medical attention or current need for hospitalization. - Mechanical ventilation or extracorporeal membrane oxygenation requirement for COVID-19. - History of allergic or reaction to any component of the study drug formulation. - History of hypersensitivity, injection/infusion-relation reactions or severe adverse reactions following administration of a monoclonal antibody (mAb). - Co-morbidity requiring surgery within 7 days prior to study entry or is deemed life-threatening within 30 days prior to study entry. - Prior receipt of convalescent COVID-19 plasma/sera or hyperimmune globulin therapy. - Prior receipt of mAb/biologic indicated for the prevention of SARS-CoV-2, treatment of COVID-19, or expected receipt during the period of study follow-up. - Prior receipt of a COVID-19 vaccine ≤ 14 days before screening or plan to receive a COVID-19 vaccination ≤ 14 days after IMP administration at study Visit 1. - History of alcohol or drug abuse within the past 2 years. - Investigational Drugs or Devices: Treatment with investigational drug or device in another clinical trial within the last 30 days or 5 half-lives of the drug (whichever is longer) prior to screening. Note: Participation in observational studies (ie, studies that do not require medication, blood draws, or an additional intervention) is not exclusionary. Interventional trials which do not include investigational drugs (only include approved therapies), or investigational treatment regimens may be considered if the blood draw requirements and study interventions are minimal and not deemed by the Investigator to interfere with completion of the planned study sampling and follow-up. - Vulnerable persons (eg, ward of the state, kept in detention).