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The Food and Drug Administration recently allowed U.S. health care providers to use convalescent plasma to treat COVID-19, but a panel of experts convened by the National Institutes of Health undercut that authorization this week, saying there’s not enough evidence to recommend its use. 

“There are currently no data from well-controlled, adequately powered randomized clinical trials that demonstrate the efficacy and safety of convalescent plasma for the treatment of COVID-19,” stated a report from the COVID-19 Treatment Guidelines Panel, part of the National Institutes of Health. 

The seeming disagreement over the role and effectiveness of convalescent plasma in treating COVID-19 has caused confusion, especially in San Antonio, where the South Texas Blood and Tissue Center (STBTC) has been urging recovered patients to donate their plasma since April.

The blood bank is participating in a nationwide treatment development effort run by the Mayo Clinic and sponsored by the National Institutes of Health. STBTC is one of a handful of centers in the country with the ability to test the collected plasma to determine the concentration of antibodies, and it sends plasma to participating hospitals throughout the U.S. as part of the experimental trial.

Convalescent plasma therapy uses blood donated from people who have recovered from an illness and separates the plasma, which contains disease-fighting antibodies produced in response to an illness. Those antibodies may provide passive immunity to certain patients with severe forms of COVID-19.

The plasma is then injected into another patient sick with COVID-19, and the antibodies it contains can potentially help fight the virus early in an infection until the patient’s own immune system generates its own antibodies in sufficient quantities to beat back the virus.

Since April, the blood bank has sent 6,716 units of convalescent plasma to regional hospitals, including Methodist Hospital Stone Oak in San Antonio, University of Texas Southwestern Medical Center in Dallas, and the Baylor College of Medicine in Houston.

The organization is seeking 75 plasma donors a day, but is receiving closer to 40, according to Roger Ruiz, STBTC’s corporate communication specialist. 

Because there’s not yet sufficient evidence about whether using convalescent plasma is an effective treatment for COVID-19, it is not meant to be used as a treatment on its own, said Dr. Samantha Gomez Ngamsuntikul, the blood bank’s associate medical director, but used alongside other treatments, including remdesivir.

“When you look at COVID-19 and convalescent plasma, it’s just one more tool that physicians have when it comes to treating patients because there really aren’t many,” said Ngamsuntikul.

Trying convalescent plasma “is a way for us to help those patients that are severely ill because it has historically been done and is considered a safe method of treatment,” Ngamsuntikul said. “The data is evolving and I think a lot of it looks promising, but it’s just buying time while we work toward better treatment methods.”

Ngamsuntikul said initial data on the effectiveness of convalescent plasma didn’t include information on how the plasma was being used alongside other treatment methods, and instead the FDA claimed it was effective on its own due to miscommunication or misinterpretation.

Ngamsuntikul said convalescent plasma has been around for more than a century and has been used to treat many diseases, including flu, polio, measles, rabies, and hepatitis B. However, it has not been used widely in the United States in decades.

Treating patients with convalescent plasma was studied during the swine flu outbreak, the SARS outbreak, and the 2012 MERS epidemic, according to the FDA.

The data cited by the FDA in granting the emergency use authorization were based on a preliminary study of convalescent plasma from the Mayo Clinic, which compared a small subset of patients who received either a high or a low concentration of COVID-19 antibodies in the plasma. The study suggested some benefit for patients who were sick enough to be in the hospital but had not been placed on ventilators. However, there was no significant difference in death rates between those who received convalescent plasma and those who didn’t.

One other small study from China, published in August in the Journal of the American Medical Association, mirrored the Mayo research. It did not show that the plasma helped people survive COVID-19 but suggested a clinical improvement among a specific group of patients: those who were in the hospital and had trouble breathing but had not yet deteriorated to the point of needing ventilators.

Ngamsuntikul said that while patients won’t recover with convalescent plasma alone, it may be helpful for those with severe symptoms. There is also data showing that there is a benefit for those patients who receive the transfusion more frequently.

The blood bank has participated in similar studies collecting convalescent plasma, including one aimed at treating people infected with the Ebola virus, but none of them had the potential to be as large as the Mayo Clinic study on treatment for people with COVID-19 because of the number of coronavirus patients worldwide.

Ngamsuntikul said that the controversy surrounding convalescent plasma highlights the need for more randomized trials and more research into COVID-19 treatment in general. 

“For us, we’re just working on providing that plasma as one more tool but physicians who are out there transfusing it on the front lines and seeing what works best,” Ngamsuntikul said. “Because everything has happened so quickly with this pandemic, [doctors are] kind of at a loss because there really aren’t any great treatments. So, we are all working to figure it out.”

Roseanna Garza

Roseanna Garza

Roseanna Garza reports on health and bioscience for the San Antonio Report.