Hydroxychloroquine as Post-Exposure Prophylaxis Against COVID-19 Infection

Inclusion Criteria: Inclusion Criteria Cohort A: * ≥ 18 years old * Employee of healthcare organization in South Dakota or Sanford Health employee in any location and with exposure to a person with COVID-19 within the last 5 days * Occupational exposure as determined by the participant's employee health department (i.e. not wearing the proper Personal Protective Equipment (PPE)) * Criteria according to Center for Disease Control (CDC) guidelines * Community exposure (within 6 feet for at least 15 minutes) * No current symptoms attributable to COVID-19, per HCW report (fever, cough, difficulty breathing, sore throat) * No prior COVID-19 positive diagnosis (eligible if previous testing is negative and meets all other inclusion and exclusion) * Ability to provide informed consent Inclusion Criteria - Cohort B * ≥ 18 years old * High-risk person who had close contact (i.e. within 6 feet for at least 15 minutes) with a COVID-19 positive person within the last 5 days and is a South Dakota resident or high-risk person with close household contact of a COVID-19 positive Sanford employee * High-risk person defined by: * Age 18-44 with 2 or more comorbidities listed below * Age 45-79 with any comorbid condition listed below * Age 80 and above (regardless of comorbid conditions) * Co-morbid list * Congestive Heart Failure (CHF) * Chronic lung disease (Includes any of the following: asthma, chronic obstructive pulmonary disease, emphysema) * Solid organ transplant or immunosuppression (Defined as an outpatient prescription of greater than 10 mg/day of prednisone or equivalent, use of chemotherapy, or use of immunosuppressive agents for solid organ transplant or for an autoimmune disease.) * Chronic Kidney Disease or End Stage Renal Disease * Diabetes mellitus * Cardiovascular disease/Hypertension * Smoking/Vaping (currently using or history of using in the past 1 year) * Obesity (calculated by height and weight per participant report) * Hyperlipidemia * No current symptoms attributable to COVID-19 * No prior COVID-19 positive diagnosis (eligible if previous testing is negative and meets all other inclusion and exclusion) * Ability to provide informed consent * Confirmed review of concomitant medications (with emphasis on cardiac medications) Exclusion Criteria Cohort A \& B: * Known allergy to hydroxychloroquine or quinine * Known history of long QT syndrome * Known history of arrhythmia or dysrhythmia * Known current QTc \>500 ms * Known G6PD deficiency * Known history of hypoglycemia * Pregnant or Nursing by patient history * Use of any of the following concomitant medications: See Appendix D for Exclusion medication list * Concurrent diagnosis of dermatitis, porphyria, or psoriasis * History of chronic liver disease, including cirrhosis and/or diagnosis of hepatitis (infectious, idiopathic, or immune) * History of chronic kidney disease * Pre-existing retinopathy * Already taking hydroxychloroquine * Any condition or medication in the opinion of the investigator that would prohibit the use of hydroxychloroquine * Enrollment in another clinical with investigational drug or device * Inability to swallow pills * Adults unable to provide informed consent