Inclusion Criteria:  Male or female at least 12 years of age  At high risk of progressing to severe COVID-19 illness due to having one of the following underlying conditions and/or sociodemographic risk factors:  Age ≥ 55 years (with or without comorbidities), Body mass index (BMI) ≥30 kg/m² if ≥ 18 years of age or BMI ≥85th percentile for age and gender based on CDC growth charts, Chronic kidney disease, Diabetes, Immunosuppressive disease, Currently receiving immunosuppressive treatment, Cardiovascular disease (including congenital heart disease) or hypertension, Chronic lung disease (e.g., chronic obstructive pulmonary disease, moderate-to-severe asthma, interstitial lung disease, cystic fibrosis, pulmonary hypertension), Sickle cell disease, Neurodevelopmental disorders or other conditions that confer medical complexity. Positive test for SARS-CoV-2 by RT-PCR or validated rapid antigen test within 72 hours prior to enrollment in the trial (positive sample must be collected within 72 hours prior to enrollment). Presence of symptoms consistent with mild or moderate COVID-19 in the judgment of the Investigator. Onset of symptoms no more than 72 hours before enrollment in the trial. Onset of symptoms is defined as the earlier of the first time at which the subject experienced subjective fever or any respiratory symptom (headache/head congestion, throat symptoms, nasal symptoms, chest symptoms, cough). Willing and able to provide written informed consent (including assent by legal guardian if under 18 years of age) and comply with the requirements of the protocol, including completion of all protocol procedures.  Exclusion Criteria:  Persons with any clinical signs or symptoms suggestive of severe systemic illness with COVID-19, including the following:  shortness of breath at rest resting pulse ≥125 beats per minute resting respiratory rate ≥30 breaths per minute Oxygen saturation ≤ 93% on room air at sea level Immunocompetent persons who have been fully vaccinated for SARS-CoV-2, defined as having received all expected vaccine doses for a 2-dose or single-dose series at least two weeks prior to onset of symptoms. Females of childbearing potential who are either pregnant or sexually active without the use of birth control. Subjects residing in the same household with another subject participating in the study. Treatment with any investigational drug or vaccine therapy within 30 days prior to screening. Receipt of monoclonal antibody therapy for COVID-19 within the preceding 90 days. Receipt of any dose of NTZ within seven days prior to screening. Known sensitivity to NTZ or any of the excipients comprising the study medication. Subjects unable to swallow oral tablets or capsules. Subjects with known severe heart, lung, neurological or other systemic disease that the Investigator believes could preclude safe participation. Subjects likely or expected to require hospitalization unrelated to COVID-19 during the study period. Subjects taking medications considered to be major CYP2C8 substrates. Subjects who, in the judgment of the Investigator, will be unlikely to comply with the requirements of this protocol.