Phase III Double-blind, Placebo-controlled Study of AZD7442 for Pre-exposure Prophylaxis of COVID-19 in Adult.

Inclusion Criteria: 1. ≥ 18 years of age at the time of signing the informed consent 2. Can benefit from passive immunization with antibodies 3. Medically stable 4. Negative result from point of care SARS-CoV-2 serology testing at screening 5. Contraceptive used by women of child bearing potential, condom used by men 6. Able to understand and comply with study requirements/procedures based on the assessment of the investigator Sub-study Inclusion criteria which are additional to those in parent study are as follows: * The participant has been randomized, dosed, and is ongoing in the PROVENT parent study and is 12±2 months post first dose of blinded IMP. * If one or more of the following apply: 1. Immunocompromised and/or may be at increased risk for an inadequate immune response to a COVID-19 vaccine. 2. In the opinion of the Investigator, are at increased risk and would benefit from a repeat dose of AZD7442. * Documented negative SARS-CoV-2 RT-PCR test collected ≤ 3 days prior to sub-study Day 1 or a negative rapid SARS-CoV-2 antigen test at screening. Exclusion Criteria: 1. Significant infection or other acute illness, including fever \>100°F (\>37.8°C) on the day prior to or day of randomization. 2. History of laboratory-confirmed SARS-CoV-2 infection or any positive SARS-CoV-2 result based on available data at screening. 3. History of infection with severe acute respiratory syndrome (SARS) or Middle East respiratory syndrome (MERS). 4. Known history of allergy or reaction to any component of the study drug formulation. 5. Previous hypersensitivity, infusion-related reaction, or severe adverse reaction following administration of a mAb. 6. Any prior receipt of investigational or licensed vaccine or other mAb/biologic indicated for the prevention of SARS-CoV-2 or COVID-19 or expected receipt during the period of study follow-up. 7. Bleeding disorder or prior history of significant bleeding or bruising following IM injections or venepuncture. 8. Any other significant disease, disorder, or finding. that may significantly increase the risk to the participant because of participation in the study, affect the ability of the participant to participate in the study, or impair interpretation of the study data. 9. 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 10. Currently pregnant or breastfeeding. 11. Blood drawn in excess of a total of 450 mL (1 unit) for any reason within 30 days prior to randomization. 12. Employees of the Sponsor involved in planning, executing, supervising, or reviewing the AZD7442 program,, clinical study site staff, or any other individuals involved with the conduct of the study, or immediate family members of such individuals. 13. In nations, states, or other jurisdictions that for legal or ethical reasons bar the enrollment of participants who lack capacity to provide their own informed consent, such subjects are excluded. Sub-study Exclusion criteria are as follows: 1. Patient have received a COVID-19 vaccination ≤ 14 days before sub-study Day1 or plan to receive a COVID-19 vaccination ≤ 14 days after sub-study Day1. (Such participants can subsequently be included in the study once they have reached \>14 days after their last dose of vaccine). 2. Patient have two or more untreated cardiac risk factors or suspected unstable cardiac disease. 3. Judgment by the Investigator that the participant should not participate in the study if the participant is unlikely to comply with study procedures, restrictions, and requirements.