A trial has begun in the UK to test whether blood plasma from Covid-19 survivors could help treat those critically ill with the disease. Plasma is a clear liquid which makes up about half of people’s blood volume and carries red and white blood cells and platelets around the body. More than 6,500 people registered their interest for the plasma donation programme, which is being led by NHS Blood and Transplant on behalf of the government. The organisation is recruiting people with the help of NHS data and inviting suitable candidates who have recovered from a confirmed case of coronavirus or had symptoms to donate plasma at its 23 main blood centres. “Recovered patients’ plasma may contain antibodies that their immune systems have produced in fighting the virus,” NHS Blood and Transplant said in a statement. “It is hoped that plasma taken no sooner than 28 days after recovery from Covid-19 will contain a high level of this neutralising antibody.” Blood had started being collected from 148 people in England so far, the BBC reported, and researchers hope antibodies found in it could become a key solution in the fight against the virus. Chinese doctors gave antibody-rich plasma from previously infected people to 15 severely ill patients earlier this year and recorded striking improvements in many of them. Doctors at Guy’s and St Thomas’ hospital in London, where the prime minister was treated for Covid-19, had collected the first plasma donations and will begin transfusion trials “in the coming weeks”, the hospital’s Biomedical Research Centre said in a statement. If the trials prove effective, NHS Blood and Transplant will begin a national programme to deliver up to 10,000 units of “convalescent plasma” a week to the NHS, enough to treat 5,000 patients each week, according to PA Media. Manu Shankar-Hari, a critical care consultant at Guy’s and St Thomas’ NHS foundation trust who is co-leading the trial with experts from NHS Blood and Transplant and the University of Cambridge, said: “As a new disease, there are no proven drugs to treat critically ill patients with Covid-19. Providing critically ill patients with plasma from patients who have recovered [...] could improve their chances of recovery.” The health and social care secretary, Matt Hancock, said: “Hundreds of people are participating in national trials already for potential treatments, and the scaling up of convalescent plasma collection means thousands could potentially benefit from it in the future.”