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COPCOV is a double-blind, randomised, placebo-controlled global study aiming to enrol 40,000 healthcare workers to determine if hydroxychloroquine and chloroquine can prevent COVID-19 that is led by the University of Oxford and the Wellcome supported Mahidol Oxford Tropical Medicine Research Unit (MORU) in Bangkok.

“There is no guarantee that we’ll soon have a widely available vaccine against COVID-19. Despite all the publicity, we still do not know if hydroxychloroquine can prevent COVID-19, but it’s really important that we find out, one way or the other. The only way to do this is to enrol a large number of participants in randomised controlled trials like COPCOV,” said Sir Jeremy Farrar, Director of the Wellcome Trust.

Previous prevention studies were too small to show conclusive evidence whether hydroxychloroquine works or not as a preventive.

“We really don’t know if hydroxychloroquine works or not in prevention or very early treatment. That question remains unanswered. The benefits found in small post-exposure treatment trials although modest could be very valuable if they were confirmed,” said Dr Will Schilling, Co-Principal Investigator of Oxford-led COPCOV clinical trial.

Early use of hydroxychloroquine could be critical.

“By the time patients are admitted to hospital virus multiplication is well past its peak and inflammation in the lungs and other complications may prove lethal. At this stage the steroid dexamethasone, which reduces inflammation, saves lives but the antivirals hydroxychloroquine and chloroquine do not,” explained MORU Director Prof Nick Day.

“However, that does not rule out that they could be effective much earlier in the illness,’”’ explained Prof Day. “Prevention is much easier than cure. The COPCOV study will find out if these drugs can prevent COVID19 or not.”

Similarly, the scientists say that safety concerns about hydroxychloroquine have been exaggerated.

“Chloroquine and hydroxychloroquine have a very good safety record in the treatment of malaria and rheumatological conditions over the past 60 years. Billions of treatments have been given. Concerns that they might cause heart arrhythmias are not supported by the evidence from the randomised trials in COVID-19, and in rheumatological conditions hydroxychloroquine has actually been shown to reduce the risk of heart arrhythmias. There is very strong evidence that the doses being evaluated for prevention in the COPCOV study are safe,” said Prof Sir Nick White, COPCOV Co-Principal Investigator.