COVID-19 Convalescent Plasma Fails to Halt Disease Progression

August 31, 2021 - COVID-19 convalescent plasma given to high-risk outpatients within one week of the onset of coronavirus symptoms does not prevent disease progression, according to a New England Journal of Medicine study. 

The randomized, multicenter clinical trial enrolled 511 patients at 48 emergency departments in 21 states being treated for COVID-19 symptoms. All patients were 50 years of age or older and had one or more risk factors for disease progression.

In the trial, patients received either one unit of convalescent plasma with a high titer of antibodies or a placebo. Plasma was collected from donors at least 14 days after clinical recovery from COVID-19. 

The primary outcome of the study was disease progression within 15 days after randomization. The secondary outcome was illness severity or death within 30 days after randomization. 

Researchers found that disease progression occurred in 30 percent (77 patients) in the convalescent plasma group and 31.9 percent (81 patients) in the placebo group. Five patients in the convalescent plasma group and one patient in the placebo group died.

Early in the pandemic, experts believed that infusion of convalescent plasma obtained from patients who recovered from the coronavirus and had SARS-CoV-2 antibodies was one strategy to reduce the severity of illness.

Plasma from recovered patients has also historically served as the most readily available source of antibodies early in epidemics or emerging infections. 

In August 2020, FDA issued an emergency use authorization for investigational convalescent plasma as a COVID-19 treatment in hospitalized patients after determining that the potential benefits outweigh the known potential risks.

But one month later, NIH challenged the use of plasma to treat the virus after finding insufficient data to recommend either for or against the treatment option. 

NIH tapped FDA’s analysis that supported the authorization of the plasma, which included data on a subset of hospitalized patients from the Mayo Clinic’s Expanded Access Program (EAP).

Researchers concluded that there was no difference in the seven-day survival rate. About 11 percent of individuals who received convalescent plasma with high titers died within seven days of transfusion. And 14 percent of those who received convalescent plasma with low antibody titers died in the same period. 

“Our results are similar to those from randomized, controlled trials involving hospitalized patients that showed no improvement in clinical outcome in those who received convalescent plasma,” researchers voiced in the study.  

“Convalescent plasma may still play a role if it is administered before the development of native antibodies,” they continued. “Future studies may consider whether convalescent plasma that is collected during different epochs and from different geographic locations during a pandemic will have different therapeutic potentials.”