• organizing an entirely no in-person contact clinical trial is feasible during a 22 COVID-19 pandemic 23
• Remote smartphone 6-lead ECG monitoring is possible even in a group unfamiliar 24 with the technology 25
• Hydroxychloroquine used prophylactically at 200 mg BID had no observable 26 cardiotoxicity 27
• Additional study using this technique is warranted to look at reliability and cost-28 effectiveness

Household members were contacted by telephone and provided consent forms via E-mail electronic signatures. Randomization was 2:1 to HCQ 200 mg BID or observation for 10 days with total follow-up of 14 days. COVID status was determined by home saliva PCR assay on days 1 and 14. Study drug was shipped to participants. Data of daily symptoms and 6-lead ECGs using a smartphone KardiaMobile® 6L application were collected.

Inclusion Criteria:

• exposure to a COVID-19-infected individual in the same household within five days of diagnosis;
• age >18 years;
• ability to give informed consent to participate in a clinical study;
• ability to swallow oral medications;
• access to a smartphone

Exclusion Criteria:

• allergy or intolerance to hydroxychloroquine (PlaquenilR);
• weight less than 85 pounds;
• eye disease affecting the retina;
• severe kidney or liver disease;
• G6PD-deficiency;
• porphyria;
• long QTc EKG abnormality or family history of this;
• other major EKG abnormalities;
• taking medications that can affect the QT interval including flecainide, amiodarone, digoxin, procainamide, propafenone, sotalol, quinidine, dofetilide, levofloxacin, ciprofloxacin, azithromycin, erythromycin, amitriptyline, doxepin, desipramine, imipramine, fluoxetine, sertraline, venlafaxine, quetiapine, haloperidol, droperidol, thioridazine, ziprasidone, furosemide, sumatriptan or zolmitriptan, cisapride, arsenic, dolasetron, or methadone;
• current pregnancy;
• current hospitalization;
• symptomatic with fever or cough;
• lack of access to a smartphone