This study looks at how well a new tablet, S-217622, works to prevent COVID-19 symptoms in people who live with someone who has COVID-19. COVID-19 is caused by the virus SARS-CoV-2. The study compares the effects of S-217622 tablets to placebo tablets, which are look-alike pills with no active medicine. There are two groups in the study: "index participants" who have COVID-19 and "study participants" who do not have COVID-19 but live in the same household. Key Points:

• The study involves taking tablets and requires regular visits to check for COVID-19 symptoms.
• The study is open to individuals aged 12 and older who have not had COVID-19 in the past six months.
• Participants must live with someone who has tested positive for COVID-19 to be eligible.

Participants must be willing to take the study tablets and keep a diary about their health. Both male and female participants must agree to use effective birth control if they are of childbearing potential. The study has specific requirements to ensure the safety of all participants.