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NIH: Convalescent Plasma Offers No Benefits as COVID-19 Treatment

An unseen person holding up a bag of blood plasma.

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Key Takeaways

  • The National Institutes of Health (NIH) has stopped a clinical trial investigating the use of convalescent plasma, citing no benefit as a COVID-19 treatment.
  • Experts say that the COVID-19 vaccines are a better option for providing immunity.
  • While it's no longer a research priority, there are studies still looking at convalescent plasma's potential as a tool to fight the new COVID-19 variants.

The National Institutes of Health (NIH) has stopped a clinical trial that was studying the use of convalescent plasma as a treatment for patients with mild to moderate COVID-19 symptoms.

The decision came after an independent data and safety monitoring board found that the convalescent plasma showed no benefit to people with COVID-19 illness.

The Hope for Convalescent Plasma

In August 2020, the U.S. Food and Drug Administration (FDA) issued an emergency use authorization (EUA) for convalescent plasma therapy for patients with COVID-19. In February 2021, it announced a revision that limited convalescent plasma's use to hospitalized COVID patients who are early in the disease progression.

William Lang, MD, medical director of WorldClinic and JobSitecare as well as a former White House physician, tells Verywell that the decision does not mean that people have stopped studying convalescent plasma. It just means that government funding can now be allocated to more prioritized treatments instead, such as COVID-19 vaccine research.

How Does Convalescent Plasma Therapy Work?

According to Lang, convalescent plasma is the oldest immune therapy, dating back to the early 20th century. It comes from people who have antibodies in their blood serum either from vaccination or natural infection.

Scientists take donated blood with antibodies and separate the blood cells, leaving a serum that contains only the antibodies. The convalescent plasma can then be transferred to an infected person to boost their immune system and speed their recovery.

Convalescent Plasma & COVID-19

When the COVID-19 pandemic began, there was limited information on the virus that first emerged in Wuhan, China. Therefore, there were not many treatments for people infected with COVID-19. Given convalescent plasma’s history with delivering antibodies, it was touted as a potential therapy for giving passive immunity. 

“Convalescent plasma provides passive immunity, meaning your body doesn’t have to do anything—someone else’s antibodies are injected, and they work until they naturally degrade,” Lang says. “With most antibodies, this is roughly a 90-day degradation period. No innate immunity is developed.”

Earlier studies had suggested potential promise for using convalescent plasma as a treatment for hospitalized patients:

  • A February 2020 article in The Lancet Infectious Diseases reported benefits of using convalescent plasma in treating viral infections—including another coronavirus (SARS).
  • A July 2020 study in Mayo Clinic Proceedings found convalescent plasma to be safe and that it reduced mortality risk when tested on 20,000 hospitalized patients.
  • A September 2020 study in Nature Medicine found that patients with severe COVID-19 illness who received the plasma and were not on a ventilator were less likely to die than patients who did not receive donated blood.

However, evidence from more recent research suggests there is limited benefit to giving COVID-19 patients convalescent plasma treatment.

  • An October 2020 study in the BMJ found no link between treatment with convalescent plasma and decreased severity of COVID-19 symptoms, nor was it found to prevent death.
  • A February 2021 study in The New England Journal of Medicine showed no significant benefits in patients with severe COVID-19 pneumonia who had received convalescent plasma compared to those who had not.

Why the NIH Trial Was Stopped

The Clinical Trial of COVID-19 Convalescent Plasma of Outpatients had enrolled 511 patients from 47 hospital emergency departments before the NIH stopped the study. The goal was to investigate the effectiveness of convalescent plasma with antibodies for SARS-CoV-2 in adults who presented to the emergency department after less than a week of experiencing mild to moderate symptoms.

All enrolled patients also had a risk factor such as obesity or chronic lung disease that made them more likely to experience severe COVID-19 infection.

The researchers followed the patients who received donated plasma for 15 days after they were enrolled in the trial. They looked at whether the patients needed further medical care, were admitted to the hospital, or died within that time.

Before the trial was halted, the researchers had found that convalescent plasma made no difference to patient care. The NIH stated that it was doubtful the results would have been altered if the trial had more patients enrolled.

The bottom line? It's not that there are any safety issues with convalescent plasma, it's just that it does not offer patients enough benefit to justify more research when there are other areas that need those resources more.

Focusing Efforts on Other Treatments & Vaccines

The interest in convalescent plasma has not totally evaporated in the absence of an NIH trial.

“Depending on where you live, there may still be ongoing studies," Lang says. "But there is no longer any mass need for convalescent plasma for COVID treatment approaches."

Given the emergence of COVID-19 variants and new research findings, it would be premature to rule out convalescent plasma therapy completely. Plus, there is still a need for convalescent plasma donations.

“This is an area of active investigation because most cases of COVID do not [undergo] genetic [sequencing] to determine which strain of SARS-CoV-2 led the infection, so convalescent plasma may contain antibodies to the newer strains,” Lang says. “Additionally, the natural response to a SARS-CoV-2 infection generates additional antibodies beyond the ones induced by the vaccine ‘spike protein’ component. Other components may help combat the virus in ways different than antibodies induced by the vaccine protein are capable of doing.”

Other treatments such as monoclonal antibodies and vaccines could prove better options. Lang says that studies on monoclonal antibodies are still ongoing but look promising so far.

Unlike convalescent plasma that only provides passive immunity, the mRNA COVID-19 vaccines give adaptive immunity by training the immune system to remember, detect, and attack any foreign invader with a spike protein. “When your body reencounters this [spike] protein, the body can rapidly rev-up the immune engines and block and/or get ahead of production of the virus," Lang says.

That said, researchers haven't given up on convalescent plasma—it's just on the back burner for now. “Importantly, there are still some studies going on as there could be unrecognized benefits to this approach to antibody therapy," Lang says. "But the main federal government funding institutions have determined that research funding would be better spent in more promising areas."

What This Means For You

Research has shown that there is no significant benefit to using convalescent plasma in patients with COVID-19. Rather, the currently approved COVID-19 vaccines are the most effective way to prevent severe infection and reduce the risk of death from the virus.

However, there is always an unmet need for blood and plasma donation. Contact your local blood bank to find out how you can help.

The information in this article is current as of the date listed, which means newer information may be available when you read this. For the most recent updates on COVID-19, visit our coronavirus news page.

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