Clinical trial finds convalescent plasma ineffective in treating COVID-19

An international study led by Canadian researchers, including the University of Alberta's Susan Nahirniak, has found that blood transfusions from patients who recovered from COVID-19 are not an effective treatment for the virus.

Nahirniak, who is the study's principal investigator in Edmonton, said the CONCOR-1 clinical trial did not demonstrate any benefit of convalescent plasma in changing the outcome for patients who were admitted to hospital due to COVID-19.

"Convalescent plasma had been found to boost immunity in patients infected with some other viral entities, including SARS, in the past," she said. The study also discovered that patients who receive convalescent plasma may become sicker.

"We are cautioning against using convalescent plasma to treat COVID-19 hospitalized patients unless they are in a closely monitored clinical trial," said Donald Arnold, co-principal investigator of the study in Toronto.

CONCOR-1 is the largest clinical trial on convalescent plasma and COVID-19. It involved 940 randomized patients at 72 hospitals across Canada, the United States, and Brazil.

Convalescent plasma was considered a potential treatment for COVID-19 patients at the beginning of the pandemic, however, the World Health Organization warned that using blood transfusions as a treatment is still an experimental therapy.

A photo of plasma bags.

A new Canadian-led study found that convalescent plasma is not an effective treatment for COVID-19 patients. (Canadian Blood Services)

Another major finding of the CONCOR-1 trial is that the levels of antibodies in the donor convalescent plasma were highly variable. Researchers said the different antibody levels have a significant impact on those receiving the treatment.

Philippe Bégin, a co-principal investigator in Montreal, said "dysfunctional antibodies could compete with the patient's own antibodies and could disrupt the mounting immune response."

Bégin explained that this study's results may be analyzed together with the results of other several similar studies to "provide more robust information and insight that will guide clinical practice and health policy globally."