RecruitingPhase 3Drug trialA Study to Learn About a Study Medicine Called Ibuzatrelvir in Adult and Adolescent Patients With COVID-19 Who Are Not Hospitalized But Are at Risk For Severe DiseaseThe purpose of the study is to evaluate whether ibuzatrelvir is effective and safe in adults and adolescents with COVID-19 who do not need to be in the hospital but who are at high risk for progression to severe disease. Eligible participants will be randomly assigned (by chance) to receive ibuzatrelvir or matching placebo orally for 5 days. Co-administration of locally available standard of care is allowed. The total duration of the study is around 6 months.