Participants fulfilling any of the following criteria are not eligible for inclusion in this study: 1. History of allergy or intolerance to chloroquine, vitamin C or any excipients. 2. Contraindication to taking chloroquine as chemoprophylaxis e.g. known epileptic, creatinine clearance < 10 mL/min, known prolonged QT syndrome, diabetes. 3. Those having previously received hydroxychloroquine for skin conditions or rheumatological diseases, chloroquine for malaria, tamoxifen, amiodarone or other drugs that may affect the retina within 30 days or 5 half-lives (whichever is longer) of study start. 4. Taking a concomitant medication (abiraterone acetate, agalsidase, amodiaquine, conivaptan, dabrafenib, dacomitinib, dapsone (systemic), enzalutamide, fusidic acid (systemic), idealisib, lanthanum, lumefantrine, mefloquine, MiFEPRIStone, Mitotane, Pimozide, QT-prolonging agents, or stiripentol) which cannot be safely stopped. 5. Participants who, in the opinion of the Investigator, do not have the ability to complete the study. For other eligibility criteria considerations, the Investigator is referred to the IB (ADFMIDI IB) for detailed information regarding warnings, precautions, contraindications, AEs, and other significant data pertaining to the use of chloroquine.

Participants fulfilling any of the following criteria are not eligible for inclusion in this study: 1. History of allergy or intolerance to chloroquine, vitamin C or any excipients. 2. Contraindication to taking chloroquine as chemoprophylaxis e.g. known epileptic, creatinine clearance < 10 mL/min, known prolonged QT syndrome, diabetes. 3. Those having previously received hydroxychloroquine for skin conditions or rheumatological diseases, chloroquine for malaria, tamoxifen, amiodarone or other drugs that may affect the retina within 30 days or 5 half-lives (whichever is longer) of study start. 4. Taking a concomitant medication (abiraterone acetate, agalsidase, amodiaquine, conivaptan, dabrafenib, dacomitinib, dapsone (systemic), enzalutamide, fusidic acid (systemic), idealisib, lanthanum, lumefantrine, mefloquine, MiFEPRIStone, Mitotane, Pimozide, QT-prolonging agents, or stiripentol) which cannot be safely stopped. 5. Participants who, in the opinion of the Investigator, do not have the ability to complete the study. For other eligibility criteria considerations, the Investigator is referred to the IB (ADFMIDI IB) for detailed information regarding warnings, precautions, contraindications, AEs, and other significant data pertaining to the use of chloroquine.