Convalescent plasma was found to be safe and effective in 19 of 25 (76%) severely ill COVID-19 patients in the first peer-reviewed study of the treatment in the United States.

The treatment, which involves infusing patients with the plasma from people who have recovered from COVID-19 and have developed antibodies, has been used in the treatment of severe microbial infections for more than 100 years, with varied success.

The findings by Eric Salazar, MD, PhD, of the Department of Pathology and Genomic Medicine at Houston Methodist Hospital in Texas, and colleagues were published on May 26 in the American Journal of Pathology.


The observational study was conducted at Houston Methodist from March 28 to April 28. Patients were eligible for the infusions if they had severe and/or life-threatening COVID-19 disease. The participants, who ranged in age from 19 to 77 years (median, 51 years; interquartile range, 42.5 – 60 years), underwent transfusion once with 300 mL of convalescent plasma.

Safety was the primary outcome; status at day 14 after transfusion was the secondary outcome. Clinical improvement was gauged on a modified World Health Organization six-point scale and on laboratory values.

Researchers found that at day 7 post transfusion, nine patients demonstrated at least a one-point improvement in clinical status; seven of those patients were discharged. By day 14, 19 patients (76%) had at least a one-point improvement, and 11 were discharged.

Salazar told Medscape Medical News he was glad to see that none of the problems that can happen with transfusions occurred in this study. Potential problems include allergic reactions ranging from mild reaction to anaphylaxis, fluid overload, and transfusion-related acute lung injury.

The findings regarding safety were consistent, he said, with other findings, including the Mayo Clinic’s expanded access protocol; the findings were published in an article on the preprint server medRxiv. In that study, which involved 5000 patients, the treatment appeared to be safe.

"It seems to be pretty well tolerated," he said.

Additionally, the authors write, "The patient outcomes in our study are similar to those recently published describing treating COVID-19 patients with remdesivir on a compassionate-use basis."

Potential There, but RCTs Still Needed

Now Salazar's team and others are working to answer other questions, including how much plasma COVID-19 patients need and how many doses should be administered. Other questions concern at which point in the illness treatment is most effective, at which point it is too late, and whether it should be used as prophylaxis or after exposure.

 "The other very important question is what titer of antibody in the units is the most effective?" he said.