Thanks. I found the following explanation at https://www.statnews.com/2020/08/23/is-convalescent-plasma-safe-and-effective/ https://www.statnews.com/2020/08/23

Thanks. I found the following explanation at https://www.statnews.com/2020/08/23/is-convalescent-plasma-safe-and-effective/ https://www.statnews.com/2020/08/23/is-convalescent-plasma-s... "A study released Aug. 13 — but not yet peer-reviewed — suggested that using convalescent plasma to treat patients with severe Covid-19 soon after their diagnosis was associated with a lower likelihood of death. But the study had serious scientific limitations that make interpreting the findings difficult. The Mayo Clinic study, which enrolled more than 35,000 patients, showed that patients who received transfusions within three days of their Covid-19 diagnosis had a seven-day death rate of 8.7%, while patients who received plasma treatment after four or more days had a mortality rate of 11.9%. The difference met the standard for statistical significance. The study didn’t include a placebo group for comparison, however, so it’s unclear exactly how impactful the plasma treatment might be. The study was sponsored by the National Institutes of Health and sought to broaden access to convalescent plasma, part of a so-called “expanded access” program not designed to definitively test how well the treatment works, but instead to quickly get it to patients. More rigorous randomized, placebo-controlled studies of convalescent plasma are ongoing."