Infusions of antibody-rich blood plasma from people who have recovered from the coronavirus, so-called convalescent plasma, failed to make a difference in a study of hospitalized patients in China, researchers reported on Wednesday in the Journal of the American Medical Association.

In a randomized trial involving 103 COVID-19 patients, convalescent plasma made no difference in the time it took to show signs of improvement or in rates of death at 28 days versus a placebo.

There were some potentially encouraging results among patients who were “severely ill” but not sick enough to be in the intensive care unit. They recovered roughly five days faster if they got the plasma treatment, and more of them improved within 28 days of starting treatment.

The study was somewhat hampered as researchers were not able to enroll as many patients as they had hoped because the epidemic started to come under control in their region, and it was stopped early. Had they been able to enroll as many patients as originally planned, the results might have been different.

An accompanying editorial by Arturo Casadevall, MD, PhD, of Johns Hopkins Bloomberg School of Public Health, and colleagues noted the positive trends and echoed the call for additional study. They also highlighted the apparent lack of any benefit in the “life-threatened” group, which suggests (along with findings from studies of other interventions) that once patients reach the stage of needing mechanical ventilation, they may be beyond help.

New, larger trials should answer many of the questions the truncated study by Liu and colleagues left hanging, the editorialists said.

Dr. Fornasari comments “This study doesn’t allow to be conclusive, but confirms positive results already seen in other anedoctical papers. The efficacy of convalescent plasma, due to neutralizing antibodies, cannot be exspected in critically ill patients, where the virus load is very low, but where the MOF symptoms are leading. In these patients, fresh frozen plasma given in high doses with plasma exchange, can be effective.