Trial to Evaluate the Efficacy and Safety of Nitazoxanide (NTZ) for Pre- and Post Exposure Prophylaxis of COVID-19 and Other Viral Respiratory Illnesses (VRI) in Healthcare Workers and Others at Increased Risk of SARS-CoV-2 Infection

Inclusion Criteria:

1. Males and females at least 18 years of age or of legal consenting age based on localrequirements.

2. Persons at increased risk of contracting COVID-19, including:

3. Healthcare workers with known direct occupational exposure to COVID-19 within 7days prior to enrollment. A qualifying person (i) provides healthcare topatients and/or (ii) typically positions themselves within 6 feet of patients ("close contact") and (iii) is a full- time employee (average of ≥ 24hours/week) in a high contact area (Emergency Department, Intensive Care Unit,COVID-specific Care Unit, Walk-in Clinic, Paramedic/First Responder).

4. Persons participating in social activities without the practice of generallyaccepted social distancing practices at least three times per week. Qualifyingactivities include the presence of at least 10 people in close (<6 feet)proximity to each other without masks or other personal protective equipment (e.g., socializing at bars or community/social centers, in-home socialgatherings, classes or trainings, etc.). These subjects must have engaged insuch activities at least three times in the past 7 days and plan to continuethese activities during the study.

5. Must have a smartphone, tablet, computer, or other qualifying internet- enableddevice and daily internet access.

6. Occupational exposure to a person infected with SAR-CoV-2 within 7 days prior toenrollment or social interaction as defined in criterion 2(b).

7. Willing and able to provide written informed consent and comply with therequirements of the protocol, including completion of the subject diary.

Exclusion Criteria:

1. Subjects not at increased risk of contracting SARS-CoV-2 from occupational or socialbehaviors.

2. Subjects with known severe heart, lung, neurological or other systemic disease thatthe Investigator believes could preclude safe participation.

3. Subjects with a history of COVID-19 or known to have developed anti- SARS-CoV-2antibodies or received a SARS-CoV-2 vaccine.

4. Subjects who experienced a previous episode of acute upper respiratory tractinfection, otitis, bronchitis or sinusitis or received antibiotics for theseconditions or antiviral therapy for influenza within two weeks prior to andincluding study day 1.

5. Subjects residing in the same household with another family member currentlyparticipating in the study.

6. Receipt of any dose of NTZ within 7 days prior to screening.

7. Treatment with any investigational drug or vaccine therapy within 30 days prior toscreening and willing to avoid them during the course of the study.

8. Known sensitivity to NTZ or any of the excipients comprising the study medication.

9. Subjects unable to swallow oral tablets or capsules.

10. Females of childbearing potential who are either pregnant or sexually active withoutthe use of birth control. Female subjects of child-bearing potential that aresexually active must have a negative baseline pregnancy test and must agree tocontinue an acceptable method of birth control for the duration of the study and for 1 month post-treatment. A double barrier method, oral birth control pillsadministered for at least 2 monthly cycle prior to study drug administration, an (intrauterine device) IUD, or medroxyprogesterone acetate administeredintramuscularly for a minimum of one month prior to study drug administration areacceptable methods of birth control for inclusion into the study. Female subjectsare considered of childbearing potential unless they are postmenopausal (absence ofmenstrual bleeding for 1 year or 6 months if laboratory confirmation of hormonalstatus), or have had a hysterectomy, bilateral tubular ligation or bilateraloophorectomy.

11. Females who are breastfeeding.

12. Subjects with active respiratory allergies or subjects expected to requireanti-allergy medications during the study period for respiratory allergies.

13. Subjects taking medications considered to be major CYP2C8 substrates.

14. Subjects who, in the judgment of the Investigator, will be unlikely to comply withthe requirements of this protocol including completion of the subject diary.