Convalescent plasma treatment for covid-19 has been oversold by the US

Convalescent plasma is known to have been used to treat pandemic flu back in 1918. It involves collecting blood plasma – the yellow liquid component of blood stripped of its blood cells – from people who have recovered from a disease. The plasma can contain antibodies generated by the immune system to fight or prevent a future infection, although the antibody levels vary between donors. The treatment does appear to work for some infections, such as diphtheria, but research has been spotty, and there has been a lack of randomised, placebo-controlled trials, says Lise Estcourt at the University of Oxford. More recently, the treatment was found to be ineffective for Ebola. Several studies are under way to test convalescent plasma for covid-19. The largest has been run by the Mayo Clinic in the US – about 71,000 people have received treatment across 2780 hospitals over the past five months as part of a programme that enables access to experimental therapies. Based on the data collected from around 35,000 of these individuals, the researchers behind the project found that people treated with plasma containing higher levels of antibody, and those treated earlier in the course of their illness, appear less likely to die within a seven or 30-day window.