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Sarah Boseley

Men who have recovered from Covid-19 are being asked to donate plasma to be used to treat sick patients in trials because they have higher levels of virus-fighting antibodies in their blood than women.

Convalescent plasma is being trialled around the world as a possible treatment for the disease. It contains antibodies generated by the immune systems of people who have fought off the virus.

NHS Blood and Transplant, which is making the appeal for donors, says it has found that more male donors have high antibody levels in their plasma than female donors – 43 percent to 29 percent – because men have tended to become sicker.

Prof David Roberts, an associate director for blood donation at NHS Blood and Transplant, said: “Initially your immune system will try and fight off a virus with white blood cells. If you become more ill, your immune system needs to produce more antibodies that neutralise or kill the virus. Our studies and many others around the world show men with Covid-19 are more likely to become seriously ill than women. This makes them better plasma donors once they have recovered.”

Two major trials are under way in the UK. The Recovery trial, based in Oxford, is testing a number of treatments, including convalescent plasma. It has already shown that a widely available steroid, dexamethasone, reduces the death rate in the sickest patients. Patients of all ages in Recovery are eligible for convalescent plasma from the moment of admission to hospital.

A second smaller trial, Remap-Cap, is offering convalescent plasma to adults in intensive care.

Prof David Menon, an intensive care doctor at the University of Cambridge, said there had been enormous global interest in the potential of convalescent plasma. “In order for the trials to rapidly deliver a result, it is really important that we have plasma from donors with high antibody levels, so that the transfusion has the best chance of affecting the clinical course and outcome of the disease.”

Convalescent plasma has been used to treat other diseases, including Ebola.

There are 23 donation centres around the UK collecting plasma for the Covid-19 trials. The procedure takes about 45 minutes. The donor’s blood is filtered to extract the plasma in a process called apheresis, and the rest of the blood is returned to the body. Within 24 to 48 hours, the body has usually replaced the donated plasma.

Until 2019, there were some restrictions on using liquid plasma in the UK, as a result of the vCJD scandal. Blood transfusions to people born after 1996 from UK donors were banned, to protect children who had not been exposed to the blood-borne virus that caused the human variant of BSE.

That was lifted last year after a safety review found there had been no new vCJD infections from UK plasma and that the risk of it happening was very low.- The Guardian