In order to assess the efficacy of hydroxychloroquine treatment weekly for a total of 7 weeks in the prevention of COVID-19 infection, three hundred sixty (360) Healthcare workers with high risk exposure to patients infected with COVID-19 will be tested for COVID-19 infection via nasopharyngeal (NP) swab once weekly for 7 weeks. Of those, one hundred eighty (180) will receive weekly doses of hydroxychloroquine for the duration of the study. Subjects who opt not to receive the study drug will form the control group.

Inclusion Criteria:

1. Adult male and female healthcare workers ≥ 18 to ≤ 75 years of age upon study consent

2. Healthcare workers with

   • One day or more of exposure to suspect and/or positive COVID-19 patients, including but not limited to those working in the Emergency Department or Intensive Care Unit.

   OR

   • Unprotected exposure to a known positive COVID-19 patient within 72 hours of screening.

3. Afebrile with no constitutional symptoms

4. Willing and able to comply with scheduled visits, treatment plan, and other study procedures

5. Evidence of a personally signed and dated informed consent document indicating that the subject (or a legally acceptable representative) has been informed of all pertinent aspects of the study prior to initiation of any subject-mandated procedures

Exclusion Criteria:

1. Participation in other investigational clinical trials for the treatment or prevention of SARS-COV-2 infection within 30days
2. Unwilling to practice acceptable methods of birth control (both males who have partners of childbearing potential and females of childbearing potential) during Screening, while taking study drug, and for at least 30 days after the last dose of study drug is ingested Note: the following criteria follow standard clinical practice for FDA approved indications of this medication
3. Having a prior history of blood disorders such as aplastic anemia, agranulocytosis, leukopenia, or thrombocytopenia
4. Having a prior history of glucose-6-phosphate dehydrogenase (G-6-PD) deficiency
5. Having dermatitis, psoriasis or porphyria
6. Taking Digoxin, Mefloquine, methotrexate, cyclosporine, praziquantel, antacids and kaolin, cimetidine, ampicillin, Insulin or antidiabetic drugs, arrhythmogenic drugs, antiepileptic drugs, loop, thiazide, and related diuretics, laxatives and enemas, amphotericin B, high dose corticosteroids, and proton pump inhibitors, neostigmine, praziquantel, Pyridostigmine, tamoxifen citrate
7. Allergies: 4-Aminoquinolines
8. Pre-existing retinopathy of the eye
9. Has a chronic liver disease or cirrhosis, including hepatitis B and/or untreated hepatitis
10. Untreated or uncontrolled active bacterial, fungal infection
11. Known or suspected active drug or alcohol abuse, per investigator judgment
12. Women who are pregnant or breastfeeding
13. Known hypersensitivity to any component of the study drug
14. A known history of prolonged QT syndrome or history of additional risk factors for torsades de pointe (e.g., heart failure, requires a lab test , family history of Long QT Syndrome), or the use of concomitant medications that prolong the QT/QTc interval

7 weeks

• Due to the off-label use of HCQ, we were not able to incorporate randomization in our design.
• The outcome of CLI was based on self-reported symptoms, which is prone to bias.
• The trial may be under-powered as recruitment was forced to stop early at 221 instead of 360 because of the demand for and subsequent shortage of HCQ in March 2020.
• Our study participants were young and healthy compared to other prophylaxis trials, which may partially explain the low rates of COVID-19.