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Hydroxychloroquine and chloroquine may have benefit in preventing COVID-19. But we still don’t know for sure. COPCOV is the world’s largest trial trying to determine: Can hydroxychloroquine and chloroquine prevent COVID-19?

The COPCOV Trial’s position statement on “A living WHO guideline on drugs to prevent COVID-19.”
5 March 2021. Following WHO recommendations against the use of hydroxychloroquine in the prevention of COVID-19, including its use in controlled trials, we are reviewing the guideline and available evidence. We are concerned that this judgement from the authors of the guideline is scientifically unsound.
Download our full statement (PDF)
Download a summary of the 6 randomised controlled trials upon which the WHO COVID-19 guidelines on chemoprophylaxis are based (xlsx)

View video transcript

COVID-19 has caused over a million deaths. Although vaccines are being deployed, the timelines for widespread roll-out are likely to be long, particularly in areas where health systems are most fragile. Many experts anticipate that smaller outbreaks may occur in the future and that the disease is likely to stay with us for a considerable period of time. Chloroquine/ hydroxychloroquine have been in constant use for more than 60 years, are cheap, safe, well-tolerated and importantly available now, yet we still do not know, a year since the emergence of COVID-19, whether they can prevent the infection. These drugs could still be of benefit while we wait for the world’s population to be vaccinated. Chloroquine/ hydroxychloroquine could also be beneficial in future pandemics, where vaccines would not be instantly available, or if vaccines became ineffective in the current pandemic.

Front-line healthcare workers and other high-risk individuals are at increased risk of infection. It is crucial that they are protected against the disease. Adequate personal protection is key, but additional interventions could further lower the risk of infection. There are currently no drugs for the prevention of COVID-19. The World Health Organization recommends that outside the setting of a clinical trial we should not give healthcare workers any drugs claiming to prevent COVID-19 before we know that they are safe and effective.

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.

The drugs used in this study, chloroquine and hydroxychloroquine, have been shown in the laboratory to kill the novel coronavirus (SARS-CoV-2), the virus that causes COVID-19. The drugs have been in the news a lot because they have been tested in trials for the treatment of COVID-19. The two largest trials (the WHO SOLIDARITY trial and the RECOVERY trial run by the University of Oxford, UK) concluded that hydroxychloroquine is not effective for the treatment of individuals hospitalised with COVID-19, but no antiviral has proven effective at this late stage when inflammation predominates, and experts believe antivirals have a better chance if given earlier. Other trials evaluating whether the drugs may provide benefit for individuals with mild or moderate symptoms are ongoing.

The drugs have also been studied for their ability to prevent COVID-19 but most randomised controlled trials only included people already exposed to an infected contact (post-exposure prophylaxis) and all the studies were too small to give a definite answer, but have been suggestive of modest benefits in preventing COVID-19. However, currently we do not know definitively if these drugs can prevent COVID-19.

COPCOV is a very large study and the only remaining trial trying to answer the question of whether these drugs can prevent COVID-19 if given before an individual is exposed (pre-exposure prophylaxis). COPCOV aims to enrol 40,000 participants and provide a definite answer as to whether the drugs are effective and safe. Hydroxychloroquine and chloroquine are affordable and globally accessible and so if shown to work the potential for public health impact would be large, particularly in regions where vaccine deployment is likely to take many months or years.

COPCOV studies chloroquine and hydroxychloroquine for the prevention of COVID-19 before an individual is exposed or infected, which is different from the treatment of patients that already have COVID-19 or treatment of individuals who have already been exposed to an infected contact, both of whom carry a much higher load of the virus.