Chloroquine Chemorophylaxis Countermeasure against COVID-19

INTERVENTION: Oral 500mg chloroquine phosphate tablets prophylactic weekly regimen against COVID‐19 over 10 week trial period followed with plasma chloroquine levels. CONDITION: COVID‐19 Infection; ; COVID‐19 Infection Infection ‐ Other infectious diseases PRIMARY OUTCOME: Number of sick days (SDS) during the study period: The number of sick days will be obtained from participants medical records as defined as the number of days deemed 'not fit for duty/work' by their reviewing medical professional, and will be compared between participants randomised to chloroquine and vitamin C.[12 weeks post‐commencement of the IMP. Study to commence Apr 2020.] SECONDARY OUTCOME: Angiotension‐converting enzyme 2 (ACE2) polymorphisms assessed by genomic analysis will be correlated with frequency of SARS‐CoV‐2 infection sequelae.[12 weeks post‐commencement of the IMP. Study to commence Apr 2020.] Drug exposure‐protection relationship. Whole blood, pre‐dose (Day 1), end of Week 5 and Week 12 chloroquine drug concentrations will be correlated with disease protection (if any).[12 weeks post‐commencement of the IMP. Study to commence Apr 2020.] Duration of COVID‐19 symptoms: Duration of COVID‐19 will be compared between the two groups using a time to clinical improvement score.[12 weeks post‐commencement of the IMP. Study to commence Apr 2020.] Incidence of asymptomatic infections caused by SARS‐CoV‐2: The asymptomatic infections caused by SARS‐CoV‐2 will be determined by comparing baseline and post‐prophylactic phase serology samples in the two groups.[12 weeks post‐commencement of the IMP. Study to commence Apr 2020.] Incidence of symptomatic SARS‐CoV‐2 infections: The incidence of symptomatic SARS‐CoV‐2 infections will be compared in participants randomised to chloroquine or vitamin C by rt‐PCR, serology, medical records, and severity of symptoms as graded by an Investigator in accordance with CTCAE Version 5.0[12 weeks post‐commencement of the IMP. Study to commence Apr 2020.] Symptom severity of COVID‐19: Symptom severity of COVID‐19 will be compared between the two groups by rt‐PCR, serology, medical records, and severity of symptoms as graded by an Investigator in accordance with CTCAE Version 5.0[12 weeks post‐commencement of the IMP. Study to commence Apr 2020.] The incidence of specific symptoms of SARS‐CoV‐2 infections (headache, diarrhoea, abdominal pain, coryzal symptoms, arthralgia, myalgia, dry cough, productive cough, fever, shortness of breath) will be compared in participants randomised to chloroquine or vitamin C. Assessed from patient health records.[12 weeks post‐commencement of the IMP. Study to commence Apr 2020.] INCLUSION CRITERIA: Participants eligible for inclusion in this study must fulfill all of the following criteria: 1. Completion of the written informed consent process (signed) with video recording of the verbal consent process; 2. Male or female age 18 to 64 years inclusive, in general good health equivalent to Army Medical Employment Classification J22 or above. Civilian personnel would need to be in good general health as advised by their General Practitioner (GP); 3. Not previously diagnosed with COVID‐19; 4. Participant works in/in association with a healthcare facility or other high‐risk environment characterised by high level of contact with persons thought likely to be infected with respiratory viruses; 5. Possess an internet enabled smart phone capable of receiving and responding to alerts; 6. Willing and able to comply with all scheduled visits, treatment plan, laboratory tests, and other study procedures; 7. Agrees not to self‐medicate with chloro