A Phase 2/3 Postexposure Prophylaxis Study of PF-07321332/Ritonavir in Household Contacts of a Patient with COVID-19. (Pfizer 1006) Purpose To compare the efficacy of 5-day and 10-day regimens of PF-07321332/ritonavir versus placebo in preventing symptomatic RT-PCR+ SARS-CoV-2 infection in adult participants who are household contacts of a patient recently diagnosed with symptomatic Covid 19. Criteria Criteria: 1. At least 18 years old. 2. No current symptoms of Covid-19/ You cannot: Have received Covid vaccine within 6 months prior to screening. Have a history of Covid-19 within 6 months of screening. Have fever or any other symptoms of Covid-19 Have liver or kidney disease. Have any other current infection. Have cancer. Details Study process: 1. Nasopharyngeal swabs and lab drawn at select visits. 2. Patient stipend. 3. No cost of drug to patient or insurance. 4. Free Covid-19 testing. Interested in more information on clinical research? Contact WK Health System Clinical Research Department 318-212-8130 or ckay@wkhs.com Interested in more information? Contact Us: Joseph Bocchini, M.D., Principal Investigator IRB: Advarra Institutional Review Board IRB Number: Trial Type: Drug Sponsor: Pfizer