A new study shows that an experimental procedure that uses convalescent plasma—essentially blood from recovered patients—to treat COVID-19 is safe.Researchers from Mayo Clinic, Michigan State University, and Johns Hopkins University, tracked 5,000 patients who received convalescent plasma transfusions and found few side effects and low mortality in those receiving the experimental treatment.The study, a pre-print version not yet peer-reviewed, was posted Thursday on a health sciences server called Medrxiv (pdf). Pre-print studies report new medical developments that are not yet approved to be used to guide medical practice. The researchers measured the impact of convalescent plasma transfusions on hospitalized...