National convalescent plasma study shows COVID-19 therapy ineffective in high-risk patients

Doctors and nurses gather outside the door of a newly transferred COVID-19 patient room in this 2020 photo. (Photo by Louis Brems)

Convalescent plasma does not effectively prevent the progression of COVID-19 from a mild to severe form of the disease in high-risk patients, according to the results of a national clinical trial that involved University of Florida Health.

The study, called the Clinical Trial of COVID-19 Convalescent Plasma of Outpatients, or C3PO, was published online Wednesday by the New England Journal of Medicine.

The investigation provided blood plasma containing coronavirus antibodies from people who had recovered from COVID-19 to outpatients within a week of the onset of mild symptoms.

“We were hoping that the use of COVID-19 convalescent plasma would achieve at least a 10% reduction in disease progression in this group, but instead the reduction we observed was less than 2%,” said Clifton Callaway, M.D., Ph.D., the contact principal investigator for the C3PO trial and professor of emergency medicine at the University of Pittsburgh. “That was surprising to us. As physicians, we wanted this to make a big difference in reducing severe illness and it did not.” 

Lisa H. Merck, M.D., M.P.H., an associate professor who is director of the clinical trials collaborative in the UF College of Medicine’s department of emergency medicine and site principal investigator of C3PO at UF Health, said UF Health researchers continue to work on clinical trials evaluating additional therapies to treat COVID-19.

“What we achieved at UF to initiate the C3PO trial was an incredible accomplishment,” Merck said. “It was crucial for scientists to evaluate the therapy in this population of patients. I would like to thank the investigators, coordinators, nurses, residents, informatics experts, blood bank and the regulatory teams for working to execute this trial. We rapidly brought together a cross-disciplinary group of providers allowing UF Health to enroll the first two patients in the country. We would like to most importantly also extend our appreciation to those patients who chose to participate in this essential research.”

Study participants had at least one risk factor for progression to severe COVID-19, such as obesity, hypertension, diabetes, heart disease, chronic lung disease, or being over 50 years old.

C3PO enrolled 511 patients nationally and found no significant difference in disease progression between those who received convalescent plasma and those in a control group who received a placebo. Progression to a more severe form of COVID-19 occurred in 30% of those receiving the plasma compared with 31.9% in the control group, results show.

Additional studies involving convalescent plasma infused in different groups of patients are either planned or ongoing.

“We need the results of these other convalescent plasma studies to get a clearer, more conclusive picture of its value for future treatments of COVID-19,” said Simone Glynn, M.D., M.P.H., chief of the National Heart, Lung and Blood Institute’ Blood Epidemiology and Clinical Therapeutics branch, who is coordinating the trial.

C3PO is coordinated through The Strategies to Innovate Emergency Care Clinical Trials Network, or SIREN. This National Institutes of Health-funded effort seeks to improve outcomes of patients with neurologic, cardiac, respiratory, hematologic and trauma emergencies by identifying effective treatments administered in the earliest stages of critical care. The UF College of Medicine’s department of emergency medicine is one of 11 hubs for research within SIREN.

C3PO is supported by the National Heart, Lung and Blood Institute in collaboration with the Biomedical Advanced Research and Development Authority. Research was led by investigators at the University of Michigan, the University of Pittsburgh, the Medical University of South Carolina and Stanford Medicine.


Learn more about UF Health's efforts to combat the COVID-19 pandemic at Coronavirus.UFHealth.org.

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Bill Levesque

Science Writer

Bill Levesque joined the UF Health staff in May 2017 as a science writer covering the Institute on Aging and research of faculty physicians in the College of Medicine. He...Read More