The first UK frontline National Health Service (NHS) worker will be enrolled as a participant into COPCOV, the largest multinational interventional clinical study into the prevention of COVID-19 using the investigational medicine hydroxychloroquine.

Enrolment begins on Thursday at the Brighton and Sussex University Hospitals and at the John Radcliffe Hospital in Oxford, the first of 20 UK hospitals to participate in this trial involving the anti-malaria drug.

Under the multinational plan, chloroquine, hydroxychloroquine or a placebo will be given to more than 40,000 healthcare workers from the UK and Europe, Africa, Asia and South America. It will test whether the drugs can prevent healthcare workers exposed to the virus from contracting it.

Accord Healthcare, a UK-based medicines manufacturer, said it has donated over 2 million tablets to enable the "landmark trial" to go ahead.

"Based on the known pharmacology of hydroxychloroquine, coupled with the emerging knowledge surrounding SARS-CoV-2 [novel coronavirus] viral replication and COVID-19 pathophysiology, we were very keen to test the effectiveness of this molecule in a preventative, rather than late-stage treatment setting," said Dr Anthony Grosso, Vice President and Head of Scientific Affairs, Accord Europe, Middle East and North Africa.

"A large-scale, prospective, randomised, double-blind clinical trial in a high-risk setting is the only way to robustly determine if this medicine can lessen or prevent human infection. Previous studies have not adequately tested this hypothesis; the results of COPCOV are therefore of critical importance to public health," he said.

The company said it is working on manufacturing the required hydroxychloroquine and matching-placebo for the study, which comes amid criticism of US President Donald Trump who admitted to using the drug as a preventive medicine despite it being unproven to be effective against the deadly virus and despite warnings that it may be unsafe.