Former coronavirus hospital patients are being urged to donate plasma as part of a major trial.
Research is being carried out to assess whether convalescent plasma donations can be transfused into patients who are struggling to develop their own immune response.
NHS Blood and Transplant (NHSBT), which is collecting the plasma for the trial, said people who were treated in hospital for COVID-19 produce the most antibodies, which makes them priority plasma donors.
The plasma from former patients is rich in the antibodies that develop as a person recovers from an illness.
It is then transfused into people who are seriously ill with COVID-19 and struggling to develop their own antibodies.
Being treated with convalescent plasma could become widespread practice in hospitals if the trial is a success.
Read more via Sky News