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Plasma bag next to donor © NHSBT

A large study of over 2000 COVID-19 patients has found that giving critically ill patients blood plasma from recovered COVID-19 patients did not significantly reduce deaths, or the need for intensive care support such as being put on a ventilator machine.

However, the results followed a slightly different pattern for the 126 patients who had immune system deficiencies. This group of patients appeared to do slightly better with the convalescent plasma treatment, compared to the standard treatment, but the number of patients were too small to make a definitive statement.

The study, published in the journal JAMA, is part of the ongoing Randomized, Embedded, Multifactorial, Adaptive Platform Trial for Community-Acquired Pneumonia (REMAP-CAP), a large international trial with over 300 trial centres in 21 countries.

The study’s first author, Dr Lise Estcourt, a researcher at the Radcliffe Department of Medicine and Director of NHS Blood and Transplant’s Clinical Trials Unit, said “Previous studies on the use of convalescent plasma as a treatment have either not systematically randomized patients to different treatment groups, or as with the RECOVERY trial, focussed on severely ill rather than critically ill patients.”

“This is the first study to demonstrate that convalescent plasma from recovered patients is not an effective treatment for critically ill patients either.”

Critically ill patients require intensive care levels of support (such as a machine to help support breathing) or need drugs to maintain normal blood pressure.

The results of the study are in keeping with both the RECOVERY trial and a previous meta-analysis, both of which also found no benefit of convalescent plasma for patients hospitalised with COVID-19.

“Our hope is that these definitive results will help inform health policy and guidelines for the treatment of COVID-19 and planning for future trials”, said senior author Professor David Roberts, a researcher at the Oxford University Radcliffe Department of Medicine and a Medical Director at NHS Blood and Transplant

Convalescent plasma is an easily available treatment even in low-resource settings and so it is still important to look for benefits of convalescent plasma in specific groups of patients. Although our results show that it is ineffective in reducing patient deaths overall, there was a trend towards benefit in patients who had weakened immune systems.
- Professor David Roberts

The researchers will now explore if people with immune system deficiencies (such as people having chemotherapy) could still benefit from convalescent plasma treatment for COVID-19.

“It could be that patients with an impaired immune system, who are unable to mount an effective immune response, could still benefit from the antibodies present in blood plasma from COVID-recovered patients”, said Dr Estcourt. “We can use convalescent plasma from donors who have been vaccinated and have very high levels of antibodies against the virus.”

The international research team which carried out this work worked with blood services in the UK, Canada, the US and Australia – see the published paper for a full list of contributors.

The researchers received funding from NIHR, the UK Department of Health and Social Care, the European Union, the Minderoo Foundation, the Health Research Council of New Zealand, the Canadian Institutes of Health Research, the Australian Government National Health and Medical Research Council, the Health Research Board, Ireland, and the Breast Cancer Research Foundation.

The researchers also wish to thank the many volunteers who donated blood plasma for these studies.