True Blood?

It is certainly worth doing trials (underway in both the UK and the USA) to establish whether transfusing serum from people, who have recovered from a Covid-19 infection, can help people struggling in hospital with the disease (https://www.theguardian.com/society/2020/apr/20/uk-trial-coronavirus-treatments-using-blood-from-survivors). This is a long-established approach (depending on boosting the antibodies to the virus) and was reportedly  trialled in the early stages of the pandemic in China with anecdotal success. The difficulty, of course, is that it would be ethically difficult to do a fully-controlled double-blind study in which some seriously ill patients received plasma from people who had not had the disease (and the physicians were initially unaware which serum had been given to which patient). We will have to rely on the percentages of recovery compared to groups receiving no transfusions. It will be difficult to ensure that the experimental and the 'control' groups are well-matched in other respects (in terms of age, gender, ethnicity, severity of disease and levels of medical and nursing care). I suspect that very large groups will be needed.