The main purpose of this study is to test an investigational drug known as VYD2311, which is being developed to lower the risk of getting COVID-19. VYD2311 is a monoclonal antibody that attaches to the virus that causes COVID-19 and helps block it from entering your cells. It is being tested in adults and adolescents at least 12 years old. Participants in this study will be given a "study drug" that will be either VYD2311 or placebo. The study drug will be given as a shot into the muscle in the participant's upper thigh or upper arm once a month with a total of 3 shots during the study. This study will help researchers see how well VYD2311 works to prevent COVID-19 during the 90 days after the first shot. The study will also look at the safety and tolerability of VYD2311, how the study drug is processed by the body (pharmacokinetics), how the immune system reacts to the study drug (immunogenicity), and how well VYD2311 can block the virus from infecting cells (neutralization). To do these tests, your blood will be drawn at certain times during the study.