Chloroquine/ Hydroxychloroquine Prevention of Coronavirus Disease (COVID-19) in the Healthcare Setting

The study is a double-blind, randomised, placebo-controlled trial that will be conducted primarily in healthcare settings and other facilities directly involved in COVID-19 case management. We will recruit healthcare workers and other persons at risk of contracting COVID-19, who can be followed reliably for 5 months. The initial aim was to recruit 40,000 participants and we predict an average of 400-800 participants per site in 50-100 sites. The participant will be randomised to receive either chloroquine or placebo (1:1 randomisation), or to hydroxychloroquine or placebo (1:1 randomisation). A loading dose of 10mg base/kg (four 155mg tablets for a 60kg subject), followed by 155 mg daily (250mg chloroquine phosphate salt/ 200mg hydroxychloroquine sulphate) will be taken for 3 months. If the participant is diagnosed with COVID-19, they will take continue to take the study medication until: * 90 days after enrolment (i.e., completion of kit) * hospitalised due to COVID-19 disease (i.e., not for quarantine purposes) in which case they will stop, or * advised to stop by their healthcare professional for other reasons Episodes of symptomatic respiratory illness, including symptomatic COVID-19, and clinical outcomes will be recorded in the Case Record Form during the follow-up period. This study is funded by Wellcome Trust Grant reference 221307/Z/20/Z.