Treatment shows ‘huge promise’ but further clinical trials called for

Q What is convalescent plasma therapy?

A Plasma is a clear, yellowish liquid that makes up about half of blood volume and carries red and white blood cells and platelets around the body. When someone recovers from a virus their plasma contains antibodies against that specific disease.

Doctors can harvest the plasma, isolate the Covid-19 antibodies and give it to patients in the early stages of the infection. The technique has been used in diseases such as Ebola.

Q Does the treatment work?

A Studies in the US have shown that the treatment is effective, although UK scientists have questioned the robustness of the evidence. A trial involving more than 35,000 patients showed that patients who received plasma within three days of diagnosis had a seven day death rate of 8.7 per cent, while those who received plasma after four or more days had a mortality rate of 11.9 per cent.

However, commentators have pointed out this study did not include a control group. Martin Landray, professor of medicine and epidemiology at the University of Oxford and one of the leaders of the UK’S Recovery trial, said the therapy showed “huge promise”. “However, there is a huge gap between theory and proven benefit. That is why randomised clinical trials are so important. At present, we simply don’t know if it works,” he said.

Q Are trials being carried out in the UK?

A NHS Blood and Transplant is currently appealing for patients who have recovered from Covid-19 to donate their plasma for a UK trial, led by the Recovery team. Men in particular are being targeted as they have higher antibody levels in their blood than women.

Q How does the convalescent plasma therapy compare to other treatments? A So far, only the steroid dexamethasone has been shown to be effective at treating coronavirus, reducing the rate of death among people on ventilators by a third.

All other treatments are currently being used either experimentally or as part of a clinical trial.

Dexamethasone is used in the latter stages of the disease while plasma can be administered earlier on, hopefully preventing patients developing severe symptoms. There is hope that monoclonal antibodies – also derived from patients who have recovered – will also be effective.

Results from trials are expected in the autumn.