1. Has at least 1 characteristic or underlying medical condition (selfreport is acceptable) associated with an increased risk of developing severe illness from COVID-19 including: ≥ 65 years of age, BMI >30 kg/m2, Current smoker (cigarette smoking within the past 30 days) and history of at least 100 lifetime cigarettes, Chronic lung disease (if asthma, requires daily prescribed therapy), Known diagnosis of hypertension, CVD, defined as history of any of the following: myocardial infarction, stroke, TIA, HF, angina with prescribed nitroglycerin, CABG, PCI, carotid endarterectomy, and aortic bypass, Type 1 or Type 2 diabetes mellitus, CKD, Sickle cell disease, Neurodevelopmental disorders (eg, cerebral palsy, Down's syndrome) or other conditions that confer medical complexity (eg, genetic or metabolic syndromes and severe congenital anomalies), Active cancer other than localized skin cancer, including those requiring treatment (including palliative treatment), as long as the treatment is not among the prohibited medications that must be administered/continued during the trial period, Medical-related technological dependence (eg, CPAP [not related to COVID-19]). 2.Immunosuppressive disease (eg, bone marrow or organ transplantation or primary immune deficiencies) OR prolonged use of immune-weakening medications: Has received corticosteroids equivalent to prednisone ≥20 mg daily for at least 14 consecutive days within 30 days prior to study entry, Has received treatment with biologics (eg, infliximab, ustekinumab, etc.), immunomodulators (eg, methotrexate, 6MP, azathioprine, etc), or cancer chemotherapy within 90 days prior to study entry', HIV infection with CD4+ cell count <200/mm3. 3. History of hospitalization for the medical treatment of COVID-19. 4. Current need for hospitalization or anticipated need for hospitalization within 48 hours after randomization in the clinical opinion of the site investigator (see Section 8.1.2). 5. Prior to current disease episode, any confirmed SARS-CoV-2 infection, as determined by a molecular test (antigen or nucleic acid) from any specimen collection. 6. Known medical history of active liver disease (other than nonalcoholic hepatic steatosis), including chronic or active hepatitis B or C infection, primary biliary cirrhosis, Child-Pugh Class B or C or acute liver failure. 7. Receiving dialysis or have known renal impairment. 8. Known HIV infection with viral load > 400 copies/mL or taking prohibited medications for HIV treatment (Appendix 8). 9. Suspected or confirmed concurrent active systemic infection other than COVID-19 that may interfere with the evaluation of response to the study intervention. 10. Any comorbidity requiring hospitalization and/or surgery within 7 days prior to study entry, or that is considered life threatening within 30 days prior to study entry, as determined by the investigator. 11. History of hypersensitivity or other contraindication to any of the components of the study intervention, as determined by the investigator. 12. Other medical or psychiatric condition including recent (within the past year) or active suicidal ideation/behavior or laboratory abnormality that may increase the risk of study participation or, in the investigator's judgment, make the participant inappropriate for the study. 13. Current or expected use of any medications or substances that are highly dependent on CYP3A4 for clearance and for which elevated plasma concentrations may be associated with serious and/or lifethreatening events during treatment and for 4 days after the last dose of PF-07321332/ritonavir (see Appendix 8). 14. Concomitant use of any medications or substances that are strong inducers of CYP3A4 are prohibited within 28 days prior to first dose of PF-07321332/ritonavir and during study treatment (see Appendix 8). 15. Has received or is expected to receive monoclonal antibody treatment, antiviral treatment (eg, molnupiravir) or convalescent COVID-19 plasma. 16. Has received any SARS-CoV-2 vaccination within 12 months of screening. Note: Participants entering the study must not receive any dose of a SARS-CoV-2 vaccine prior to Day 34. Please refer to Protocol section 5.2 for remaining exclusion criteria

1. Has at least 1 characteristic or underlying medical condition (selfreport is acceptable) associated with an increased risk of developing severe illness from COVID-19 including: ≥ 65 years of age, BMI >30 kg/m2, Current smoker (cigarette smoking within the past 30 days) and history of at least 100 lifetime cigarettes, Chronic lung disease (if asthma, requires daily prescribed therapy), Known diagnosis of hypertension, CVD, defined as history of any of the following: myocardial infarction, stroke, TIA, HF, angina with prescribed nitroglycerin, CABG, PCI, carotid endarterectomy, and aortic bypass, Type 1 or Type 2 diabetes mellitus, CKD, Sickle cell disease, Neurodevelopmental disorders (eg, cerebral palsy, Down's syndrome) or other conditions that confer medical complexity (eg, genetic or metabolic syndromes and severe congenital anomalies), Active cancer other than localized skin cancer, including those requiring treatment (including palliative treatment), as long as the treatment is not among the prohibited medications that must be administered/continued during the trial period, Medical-related technological dependence (eg, CPAP [not related to COVID-19]). 2.Immunosuppressive disease (eg, bone marrow or organ transplantation or primary immune deficiencies) OR prolonged use of immune-weakening medications: Has received corticosteroids equivalent to prednisone ≥20 mg daily for at least 14 consecutive days within 30 days prior to study entry, Has received treatment with biologics (eg, infliximab, ustekinumab, etc.), immunomodulators (eg, methotrexate, 6MP, azathioprine, etc), or cancer chemotherapy within 90 days prior to study entry', HIV infection with CD4+ cell count <200/mm3. 3. History of hospitalization for the medical treatment of COVID-19. 4. Current need for hospitalization or anticipated need for hospitalization within 48 hours after randomization in the clinical opinion of the site investigator (see Section 8.1.2). 5. Prior to current disease episode, any confirmed SARS-CoV-2 infection, as determined by a molecular test (antigen or nucleic acid) from any specimen collection. 6. Known medical history of active liver disease (other than nonalcoholic hepatic steatosis), including chronic or active hepatitis B or C infection, primary biliary cirrhosis, Child-Pugh Class B or C or acute liver failure. 7. Receiving dialysis or have known renal impairment. 8. Known HIV infection with viral load > 400 copies/mL or taking prohibited medications for HIV treatment (Appendix 8). 9. Suspected or confirmed concurrent active systemic infection other than COVID-19 that may interfere with the evaluation of response to the study intervention. 10. Any comorbidity requiring hospitalization and/or surgery within 7 days prior to study entry, or that is considered life threatening within 30 days prior to study entry, as determined by the investigator. 11. History of hypersensitivity or other contraindication to any of the components of the study intervention, as determined by the investigator. 12. Other medical or psychiatric condition including recent (within the past year) or active suicidal ideation/behavior or laboratory abnormality that may increase the risk of study participation or, in the investigator's judgment, make the participant inappropriate for the study. 13. Current or expected use of any medications or substances that are highly dependent on CYP3A4 for clearance and for which elevated plasma concentrations may be associated with serious and/or lifethreatening events during treatment and for 4 days after the last dose of PF-07321332/ritonavir (see Appendix 8). 14. Concomitant use of any medications or substances that are strong inducers of CYP3A4 are prohibited within 28 days prior to first dose of PF-07321332/ritonavir and during study treatment (see Appendix 8). 15. Has received or is expected to receive monoclonal antibody treatment, antiviral treatment (eg, molnupiravir) or convalescent COVID-19 plasma. 16. Has received any SARS-CoV-2 vaccination within 12 months of screening. Note: Participants entering the study must not receive any dose of a SARS-CoV-2 vaccine prior to Day 34. Please refer to Protocol section 5.2 for remaining exclusion criteria

1. Has at least 1 characteristic or underlying medical condition (selfreport is acceptable) associated with an increased risk of developing severe illness from COVID-19 including: ≥ 65 years of age, BMI >30 kg/m2, Current smoker (cigarette smoking within the past 30 days) and history of at least 100 lifetime cigarettes, Chronic lung disease (if asthma, requires daily prescribed therapy), Known diagnosis of hypertension, CVD, defined as history of any of the following: myocardial infarction, stroke, TIA, HF, angina with prescribed nitroglycerin, CABG, PCI, carotid endarterectomy, and aortic bypass, Type 1 or Type 2 diabetes mellitus, CKD, Sickle cell disease, Neurodevelopmental disorders (eg, cerebral palsy, Down's syndrome) or other conditions that confer medical complexity (eg, genetic or metabolic syndromes and severe congenital anomalies), Active cancer other than localized skin cancer, including those requiring treatment (including palliative treatment), as long as the treatment is not among the prohibited medications that must be administered/continued during the trial period, Medical-related technological dependence (eg, CPAP [not related to COVID-19]). 2.Immunosuppressive disease (eg, bone marrow or organ transplantation or primary immune deficiencies) OR prolonged use of immune-weakening medications: Has received corticosteroids equivalent to prednisone ≥20 mg daily for at least 14 consecutive days within 30 days prior to study entry, Has received treatment with biologics (eg, infliximab, ustekinumab, etc.), immunomodulators (eg, methotrexate, 6MP, azathioprine, etc), or cancer chemotherapy within 90 days prior to study entry', HIV infection with CD4+ cell count <200/mm3. 3. History of hospitalization for the medical treatment of COVID-19. 4. Current need for hospitalization or anticipated need for hospitalization within 48 hours after randomization in the clinical opinion of the site investigator (see Section 8.1.2). 5. Prior to current disease episode, any confirmed SARS-CoV-2 infection, as determined by a molecular test (antigen or nucleic acid) from any specimen collection. 6. Known medical history of active liver disease (other than nonalcoholic hepatic steatosis), including chronic or active hepatitis B or C infection, primary biliary cirrhosis, Child-Pugh Class B or C or acute liver failure. 7. Receiving dialysis or have known renal impairment. 8. Known HIV infection with viral load > 400 copies/mL or taking prohibited medications for HIV treatment (Appendix 8). 9. Suspected or confirmed concurrent active systemic infection other than COVID-19 that may interfere with the evaluation of response to the study intervention. 10. Any comorbidity requiring hospitalization and/or surgery within 7 days prior to study entry, or that is considered life threatening within 30 days prior to study entry, as determined by the investigator. 11. History of hypersensitivity or other contraindication to any of the components of the study intervention, as determined by the investigator. 12. Other medical or psychiatric condition including recent (within the past year) or active suicidal ideation/behavior or laboratory abnormality that may increase the risk of study participation or, in the investigator's judgment, make the participant inappropriate for the study. 13. Current or expected use of any medications or substances that are highly dependent on CYP3A4 for clearance and for which elevated plasma concentrations may be associated with serious and/or lifethreatening events during treatment and for 4 days after the last dose of PF-07321332/ritonavir (see Appendix 8). 14. Concomitant use of any medications or substances that are strong inducers of CYP3A4 are prohibited within 28 days prior to first dose of PF-07321332/ritonavir and during study treatment (see Appendix 8). 15. Has received or is expected to receive monoclonal antibody treatment or convalescent COVID-19 plasma. 16. Has received any SARS-CoV-2 vaccination within 12 months of screening. Note: Participants entering the study must not receive any dose of a SARS-CoV-2 vaccine prior to Day 34. Please refer to Protocol section 5.2 for remaining exclusion criteria

1. Has at least 1 characteristic or underlying medical condition (selfreport is acceptable) associated with an increased risk of developing severe illness from COVID-19 including: ≥ 65 years of age, BMI >30 kg/m2, Current smoker (cigarette smoking within the past 30 days) and history of at least 100 lifetime cigarettes, Chronic lung disease (if asthma, requires daily prescribed therapy), Known diagnosis of hypertension, CVD, defined as history of any of the following: myocardial infarction, stroke, TIA, HF, angina with prescribed nitroglycerin, CABG, PCI, carotid endarterectomy, and aortic bypass, Type 1 or Type 2 diabetes mellitus, CKD, Sickle cell disease, Neurodevelopmental disorders (eg, cerebral palsy, Down's syndrome) or other conditions that confer medical complexity (eg, genetic or metabolic syndromes and severe congenital anomalies), Active cancer other than localized skin cancer, including those requiring treatment (including palliative treatment), as long as the treatment is not among the prohibited medications that must be administered/continued during the trial period, Medical-related technological dependence (eg, CPAP [not related to COVID-19]). 2.Immunosuppressive disease (eg, bone marrow or organ transplantation or primary immune deficiencies) OR prolonged use of immune-weakening medications: Has received corticosteroids equivalent to prednisone ≥20 mg daily for at least 14 consecutive days within 30 days prior to study entry, Has received treatment with biologics (eg, infliximab, ustekinumab, etc.), immunomodulators (eg, methotrexate, 6MP, azathioprine, etc), or cancer chemotherapy within 90 days prior to study entry', HIV infection with CD4+ cell count <200/mm3. 3. History of hospitalization for the medical treatment of COVID-19. 4. Current need for hospitalization or anticipated need for hospitalization within 48 hours after randomization in the clinical opinion of the site investigator (see Section 8.1.2). 5. Prior to current disease episode, any confirmed SARS-CoV-2 infection, as determined by a molecular test (antigen or nucleic acid) from any specimen collection. 6. Known medical history of active liver disease (other than nonalcoholic hepatic steatosis), including chronic or active hepatitis B or C infection, primary biliary cirrhosis, Child-Pugh Class B or C or acute liver failure. 7. Receiving dialysis or have known renal impairment. 8. Known HIV infection with viral load > 400 copies/mL or taking prohibited medications for HIV treatment (Appendix 8). 9. Suspected or confirmed concurrent active systemic infection other than COVID-19 that may interfere with the evaluation of response to the study intervention. 10. Any comorbidity requiring hospitalization and/or surgery within 7 days prior to study entry, or that is considered life threatening within 30 days prior to study entry, as determined by the investigator. 11. History of hypersensitivity or other contraindication to any of the components of the study intervention, as determined by the investigator. 12. Other medical or psychiatric condition including recent (within the past year) or active suicidal ideation/behavior or laboratory abnormality that may increase the risk of study participation or, in the investigator's judgment, make the participant inappropriate for the study. 13. Current or expected use of any medications or substances that are highly dependent on CYP3A4 for clearance and for which elevated plasma concentrations may be associated with serious and/or lifethreatening events during treatment and for 4 days after the last dose of PF-07321332/ritonavir (see Appendix 8). 14. Concomitant use of any medications or substances that are strong inducers of CYP3A4 are prohibited within 28 days prior to first dose of PF-07321332/ritonavir and during study treatment (see Appendix 8). 15. Has received or is expected to receive monoclonal antibody treatment or convalescent COVID-19 plasma. 16. Has received any SARS-CoV-2 vaccination within 12 months of screening. Note: Participants entering the study must not receive any dose of a SARS-CoV-2 vaccine prior to Day 34. Please refer to Protocol section 5.2 for remaining exclusion criteria