On December 6, 2021, the WHO revised its “
The WHO now recommends against the use of convalescent plasma in treating people with nonsevere, severe, and critical COVID-19 outside of clinical trials for people with severe or critical infections of the SARS-CoV-2 virus.
The WHO’s Guideline Development Group based their conclusions on research involving 16 trials and 16,236 patients with nonsevere, severe, and critical forms of COVID-19.
However, not all experts agree with the WHO’s conclusions. Dr. Arturo Casadevall, director of Molecular Microbiology and Immunology at Johns Hopkins Bloomberg School of Public Health, told Medical News Today:
“I don’t know how the WHO made its decision, but I feel that they erred. I strongly disagree with the WHO recommendation, which seems to ignore that there is considerable published evidence for convalescent plasma efficacy.”
– Dr. Casadevall
“After 1.5 years, we are learning how to use this complex but cheap and readily available therapy. The emerging view is that convalescent plasma is effective when used early in the course of [the] disease, with plasma units that contain high titers of antibody and are sourced locally.”
The idea behind convalescent plasma is that a person who has recovered from COVID-19 would be in possession of antibodies with which they fought off the disease.
By donating their blood plasma to someone else, those antibodies would be transferred to that second individual.
This could be especially helpful when both people have had exposure to the same SARS-CoV-2 variant, since those antibodies have already succeeded in overcoming it. “Convalescent plasma,” noted Dr. Casadevall, “is the only therapy that adapts to the [variants], since anyone who recovers from a variant infection can give plasma to treat that variant.”
The WHO does not find that the treatment endangers patients.
The WHO says: “In nonsevere patients, convalescent plasma does not result in an important impact on mortality. Convalescent plasma probably does not impact mechanical ventilation. There were no data evaluating the risk of hospitalization with convalescent plasma, and therefore the impact is very uncertain.”
“Convalescent plasma probably does not result in important increases in risks of transfusion-related acute lung injury (TRALI), transfusion-associated circulatory overload (TACO), or allergic reactions.”
However, the lack of evidence of convalescent plasma’s efficacy led the WHO to conclude, “almost all well-informed patients would choose against receiving convalescent plasma based on available evidence regarding relative benefits and harms.”
In addition, “From a population perspective, feasibility, acceptability, equity, and cost are other important elements to take into account.”
“Convalescent plasma has been widely used in the United States, and we have estimated that it saved about 100,000 lives,” said Dr. Casadevall, as reported in a June 2021 study for which he was the lead author.
Dr. Casadevall asserted that much research has been “focused on very sick patients who could not be helped by [an] antibody.”
“Hence,” he said, “these trials created a futile cycle, where convalescent plasma was tested in conditions it could not work and then people concluded that it did not work.”
Medical News Today asked Dr. Casadevall about recent research finding convalescent plasma to be ineffective. This study was not among the 16 studies that the WHO considered. He replied that he and his colleagues “think that the results of this trial were not interpreted correctly.”
“In fact,” he continued, “we have posted a critique of that trial, reinterpreting the data and finding that early administration of plasma had an efficacy of 35%.”
Dr. Casadevall authored the above critique together with his colleagues at The COVID-19 Convalescent Plasma Project Leadership Group.
Dr. Casadevall told Medical News Today he is especially concerned about the timing of the WHO’s revised guidance:
“It is very unfortunate that the WHO issued their recommendation during a time when the world is facing [the new variant] Omicron, and convalescent plasma remains one of the best therapeutic options until new monoclonal antibodies and oral antivirals are available.”
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