Inclusion Criteria The main inclusion criteria include, but are not limited to, the following: * Is a person of any sex/gender, ≥18 years of age * Has documentation of SARS-CoV-2 infection with sample collection ≤4 days before randomization * Has initial onset of signs/symptoms attributable to COVID-19 for ≤4 days before the day of randomization and ≥2 of the following signs/symptoms attributable to COVID-19 on the day of randomization: cough, sore throat, nasal congestion, shortness of breath or difficulty breathing on exertion, muscle or body aches, fatigue, fever >38,0 °C or chills, nausea or vomiting or diarrhea, change in sense of smell or change in sense of taste or headache * Has ≥1 of the following characteristics or medical conditions associated with increased risk of severe illness from COVID-19: * Advanced age ≥75 years of age * Immunocompromised * Neurocognitive or physical disability * Has ≥3 characteristics or medical conditions that increase the risk of severe illness due to COVID-19 (e.g. e.g., chronic lung disease, obesity with body mass index ≥35, diabetes) * Cannot receive treatment with nirmatrelvir/ritonavir (NMV/r) due to one or more of the following: * Are receiving drug(s) highly dependent on cytochrome P450 3A (CYP3A) for clearance and for which elevated concentrations are associated with serious and/or life-threatening consequences or drug(s) with a clinically significant drug interaction for which co-administration is not possible * Are receiving potent CYP3A inducers where significantly reduced plasma concentrations of nirmatrelvir or ritonavir may be associated with the possibility of loss of virologic response and possible resistance * Have severe renal or hepatic impairment * Have experienced previous adverse reactions or hepatotoxicity to NMV/r that would preclude future use * Have uncontrolled HIV infection * Have known or suspected resistance to NMV/r * NMV/r is not approved/authorized in the participant's country is or is not accessible to the participant (e.g. e.g., drug shortages) Inclusion note: Participants may receive remdesivir as standard of care in addition to molnupiravir or placebo. If remdesivir is available and clinically appropriate according to local clinical practice, researchers will attempt to ensure that those most vulnerable to severe COVID-19 receive timely access to remdesivir as the standard of care in this study. Exclusion Criteria The main exclusion criteria include, but are not limited to, the following: * Currently hospitalized or expected to require hospitalization for COVID-19 imminently * Has received or plans to receive SARS-CoV-2-targeted antivirals or monoclonal antibodies for the current episode of COVID-19 (other than the study intervention and, if applicable, remdesivir as standard of care) * Has ≥1 of the following signs/symptoms attributable to severe or critical COVID-19: * Shortness of breath at rest * Respiratory rate ≥30 breaths per minute * Heart rate ≥125 beats per minute * Peripheral oxygen saturation (SpO2) ≤93% on room air or with supplemental oxygen for a reason other than COVID-19 that has not increased since the onset of COVID-19 signs/symptoms * Is receiving >4 liters/minute of supplemental oxygen for COVID-19 (but was not receiving supplemental oxygen prior to COVID-19), regardless of SpO2 * Has received a COVID-19 vaccine within 30 days prior to randomization * Has a history of SARS-CoV-2 infection (with or without symptoms) within 30 days prior to randomization * Has a known or suspected hypersensitivity to the active or inactive ingredients of molnupiravir