A potential COVID-19 treatment, convalescent plasma, does not improve outcomes for critically ill COVID-19 patients, a study by our scientists has found.

The study, which followed 2,000 COVID-19 patients overall, found that the treatment did not significantly reduce deaths, or the need for intensive care support in most patients. However, for a subgroup of 126 patients with documented immunosuppression, results did suggest possible benefit. It showed an 89% chance that convalescent plasma was better than usual care in immunosuppressed patients. Due to the small sample size for this subgroup of COVID-19 patients with documented immunosuppression, further research is needed to confirm its efficacy.

The study leads expressed their gratitude to the thousands of people who have had COVID-19, and came forward to donate their plasma to the study, and to the patients who participated in the study.

The ‘convalescent plasma’ treatment involves blood plasma donations from patients who have recovered from COVID-19. This plasma is transfused into COVID-19 patients whose bodies are not producing enough of their own antibodies against the virus, in an attempt to support the patients fighting the disease.

Professor Manu Shankar-Hari, a consultant in intensive care medicine at Guy’s and St Thomas’, was senior author of the paper and a co-lead on the study, along with experts from NHS Blood and Transplant, the University of Oxford and the University of Cambridge. The study was a part of the ongoing REMAP-CAP study.

Professor Shankar-Hari said: “In a new condition like COVID-19, it is vital for clinicians to know what does and what does not improve outcomes for patients. While we thought that convalescent plasma may be a promising treatment, knowing that it is not effective in most ICU patients is vital, so we can focus on identifying treatments we know do help these patients. Our study has also highlighted a subgroup of COVID-19 patients, who may benefit from the treatment, and we are pursuing that signal in future studies.”

“I want to thank the thousands of patients who came forward to donate plasma, and have helped us to understand more about this disease. We’re also incredibly grateful to the patients who participated in the research, and to their families. They took part at an incredibly stressful and difficult time, and have made a really important contribution to help patients in the future.”

The findings were published in the journal JAMA . The trial was supported by the NIHR.