Science inconclusive on use of convalescent plasma in COVID-19 patients

President Trump’s announcement that his administration would approve the emergency use of convalescent plasma in patients suffering from COVID-19 has put the government out of step with scientists who say there is no firm indication yet that such treatment actually works.

The Food and Drug Administration (FDA) late Sunday issued an emergency use authorization for convalescent plasma, allowing it to be administered to those hospitalized with COVID-19. In a letter, FDA chief scientist Denise Hinton said the agency had concluded “that it is reasonable to believe that COVID-19 convalescent plasma may be effective for the treatment” of those in the hospital.

Convalescent plasma is derived from the blood of those who have had and recovered from a virus. It uses antibodies created by the immune system to help a recipient’s body learn to fight off a pathogen on its own.

Though Trump touted convalescent plasma as a “very historic breakthrough,” it is one of the oldest tools in modern medicine, a technique that goes back to the development of the modern understanding of viruses. It has been used to treat everything from influenza to, more recently, the Ebola virus.

“Convalescent plasma therapy is actually something that’s been used for over 100 years for various infectious diseases, and it’s been effective in some and not so effective in others,” said Soumya Swaminathan, the World Health Organization’s chief scientist.

In the case of the SARS-CoV-2 virus, there are conflicting signs about whether convalescent plasma even works. Studies across the globe have given mixed signals. 

“We are far from having any definitive proof that it’s effective, clinically, and saves lives,” said Howard Koh, a public health expert at Harvard’s Chan School of Public Health and a former assistant secretary for health in the Obama administration. “This one is going to attract a lot of debate.”

The first peer-reviewed study to be published, of 103 hospitalized patients in Wuhan, China, the epicenter of the pandemic outbreak, showed no statistically significant benefits. That study was halted early because the authors could not recruit enough patients to mount a substantial trial.

Another study of 20,000 patients conducted by the Mayo Clinic in June found mortality rates declined among those who received convalescent plasma. 

The Mayo Clinic scientists cautioned that the declining mortality rate may have come because those receiving the plasma were less severely ill than the group to whom they were compared. Their study, they said, was not meant to take the place of a clinical trial.

A third study, also conducted by the Mayo Clinic, found a statistically significant benefit, though it was conducted without a control group that did not receive the plasma. That study has not been peer reviewed, leaving some to question its conclusions.

And a study in the Netherlands was halted early over concerns that the plasma was not working to reduce mortality, hospitalization or the duration of the disease. 

“The results are not conclusive. I should say the trials have been relatively small and the results in some cases point to some benefit, but have not been conclusive,” Swaminathan said Monday. “Convalescent plasma is still an experimental therapy. It should continue to be evaluated in well-designed randomized clinical trials.”

Last week, top American health officials including National Institutes of Health Director Francis Collins and Anthony Fauci, director of the National Institute of Allergy and Infectious Disease, raised objections to an emergency use authorization, The New York Times reported.

Several questions about the effectiveness of convalescent plasma treatments remain: The coronavirus causes different immune responses in people depending on the severity of their own disease, leaving it unclear whether all convalescent plasma samples would be equally effective. It is not clear at what dose the plasma should be administered. And it is not clear when someone should receive the plasma, though the studies suggest the sooner after the onset of symptoms the better.

“There is actually no standard protocol,” Koh said.

There is also no clear evidence that convalescent plasma treatment is safe. The World Health Organization said that plasma, like any other therapy, can come with risks — in the case of COVID-19, there are some signs of side effects, ranging from low-level fevers to more troubling lung damage.

“Blood plasma transfusions are not without risks, including death, and scientists should be afforded the opportunity to prove the benefits outweigh the risks,” said Benjamin Corb, director of public affairs at the American Society for Biochemistry and Molecular Biology.

Beyond health and safety, there is a risk that the FDA’s emergency use authorization will make it more difficult to determine whether convalescent plasma is actually effective. If the treatment already has authorization for use, patients will be unlikely to sign up for studies in which they might be assigned to a control group that does not receive the treatment, Koh said.

“The best way to move toward definitive outcomes is to have a randomized trial in which there’s a control group in which some people get the treatment and others don’t,” he said. The emergency use authorization “is going to hamper our abilities to ever prove definitively that convalescent plasma works, because everybody is going to want this treatment.”

Convalescent plasma is the latest potential treatment for the coronavirus that Trump has rushed to embrace before the science is clear. Trump for months pushed scientists to treat COVID-19 patients with hydroxychloroquine, even after major studies were halted prematurely when they showed no effects or negative consequences. 

Earlier this year, he publicly wondered whether the coronavirus could be killed by ultraviolet light, or by injecting disinfectant. Medical experts raced to clarify that no one should ingest cleaning supplies.

“My fear is that this announcement has shaken the confidence of the medical community,” Koh said. “This is a time to insist that the rigor and science of the decisionmaking process be held to the highest level. The future of global public health is dependent on that.”