A Study to Test Whether BI 767551 Can Prevent COVID-19 in People Who Have Been Exposed to SARS-CoV-2

Inclusion Criteria: * ≥ 18 years old, males and females * Signed and dated written informed consent in accordance with International Council on Harmonisation - Good Clinical Practice (ICH-GCP) and local legislation prior to admission to the trial * Asymptomatic for Coronavirus Disease 2019 (COVID-19) at time of screening and at randomization * Household contact with exposure to an individual with a diagnosis of Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection (i.e. exposure to the index case) * Randomization within 96 hours of collection of the index cases' positive SARS-CoV-2 diagnostic test sample (nucleic acid or antigen-based) from any respiratory tract specimen (e.g. oropharyngeal, nasopharyngeal (NP), or nasal swab, or saliva); based on test sample collection date, not the result date. * From screening and randomization, the trial participant anticipates living in the same household with the index case until protocol Day 29. * Women of childbearing potential (WOCBP)\* and men able to father a child must be ready and able to use highly effective methods of birth control per International Council on Harmonisation (ICH) M3 (R2) that result in a low failure rate of less than 1% per year when used consistently and correctly. * A woman is considered of childbearing potential (WOCBP), i.e. fertile, following menarche and until becoming post-menopausal unless permanently sterile. Permanent sterilisation methods include hysterectomy, bilateral salpingectomy and bilateral oophorectomy. Tubal ligation is NOT a method of permanent sterilisation. A postmenopausal state is defined as no menses for 24 months without an alternative medical cause. Exclusion Criteria: * Body weight of less than 40 kg * Residents of skilled nursing facilities. Definition of skilled nursing facility: assisted living facility that typically provides daily nursing care, 24-hour supervision, three meals a day, and assistance with everyday activities. * History of laboratory confirmed SARS-CoV-2 infection (e.g. antigen or nucleic acid test)at any time before screening * Active respiratory or non-respiratory symptoms consistent with COVID-19, in the opinion of the investigator * History of respiratory or non-respiratory symptoms consistent with COVID-19, within the prior 6 months to screening, in the opinion of the investigator * Participant has lived with individuals who have had previous SARS-CoV-2 infection or currently lives with individuals who have SARS-CoV-2 infection, with the exception of the index case(s) who is defined as the first individual(s) known to be infected in the household * Receipt of intravenous immunoglobulin within 12 weeks prior to Visit 2 * Receipt of COVID-19 convalescent plasma treatment at any time prior to Visit 2 * Receipt of any SARS-CoV-2 monoclonal antibody treatment at any time prior to Visit 2 * Receipt of SARS-CoV-2 vaccine at any time prior to Visit 2 * Receipt of an investigational product for COVID-19 within 5 half-lives prior to Visit 2 * Receipt of systemic steroids (e.g. prednisone, dexamethasone) within 4 weeks prior to Visit 2 unless used for chronic condition * Subjects who must or wish to continue the intake of restricted medications or any drug considered likely to interfere with the safe conduct of the trial * Any co-morbidity requiring surgery within 7 days prior to study entry, or that is considered life threatening in the opinion of investigator within 30 days prior to randomization * Have any serious concomitant systemic disease, condition or disorder that, in the opinion of the investigator, should preclude participation in this study * Subjects not expected to comply with the protocol requirements or not expected to complete the trial as scheduled (e.g. chronic alcohol or drug abuse or any other condition that, in the investigator's opinion, makes the subject an unreliable trial participant) * Currently enrolled in any other type of medical research judged not to be compatible with this study * Known allergy/sensitivity or any hypersensitivity to any of the components used in the formulation of the interventions * Previous enrolment in this trial * Women who are pregnant, nursing, or who plan to become pregnant while in the trial