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COPCOV is a randomised, placebo-controlled pre-exposure prophylaxis study to determine whether chloroquine or hydroxychloroquine prevents coronavirus disease (COVID-19).

The COPCOV study compares the drugs chloroquine and hydroxychloroquine against a placebo pill (not containing any drugs) for the prevention of COVID-19. Healthcare workers in participating centres and other individuals who are at greater risk of exposure to COVID-19 who wish to join the study must provide consent and cannot have had COVID-19 before enrolment.

Half of the participants receive the drug, the other half receive a placebo. The selection will be random. To enable unbiased assessments, neither the local study team nor the participant will know if they receive the drug or placebo tablets (“double blind”). All participants will also take the usual precautions for protection against the virus. Participants will take the study drugs each day for a period of three months, and will be followed closely to see how well the drug is tolerated, whether they contract the virus, and if they do, whether they develop mild or more severe COVID-19. If a participant develops COVID-19, they will be treated according to local treatment guidelines. The study aims to enrol 40,000 participants globally. We expect to have preliminary results available as to whether chloroquine or hydroxychloroquine can prevent COVID-19 after the middle of 2021.