Convalescent Plasma Cuts COVID-19 Hospitalizations in Half: Study

Damian McNamara, MA

December 21, 2021

Editor's note: Find the latest COVID-19 news and guidance in Medscape's Coronavirus Resource Center.

A "definitive study" from Johns Hopkins University researchers and others shows that convalescent plasma can cut hospital admissions for COVID-19 by 54% if therapy is administered within 8 days of symptom onset.

In the study of 1181 adults randomly assigned to high-titer convalescent plasma or placebo, 2.9% of people receiving the therapy were hospitalized compared to 6.3% who received placebo control plasma.

This translates to a 54% risk reduction for hospitalization with convalescent plasma.

"We have a clear difference," principal investigator David Sullivan, MD, a professor at Johns Hopkins Bloomberg School of Public Health in Baltimore, said during a a Tuesday media briefing.

"This is very good news since we are in the midst of the Omicron surge, which has defeated [some of] our major monocular antibody therapies," said Arturo Casadevall, MD, chair of the Department of Molecular Microbiology and Immunology at Johns Hopkins.

"So we have a new tool to keep people from progressing in their disease and to reduce progression or hospitalization," Casadevall said.

The findings were published as a preprint study Tuesday on medRxiv. The study has not yet been peer reviewed.

Whereas many convalescent plasma studies were done in hospitalized patients, this is one of only a handful performed in outpatients, the researchers note.

There is a regulatory catch. The FDA restricted emergency use authorization (EUA) for convalescent plasma in February 2021 to include only high-dose titer plasma and to limit the therapy to hospitalized patients with early disease or for immunocompromised people who cannot mount an adequate antibody response.

Sullivan and colleagues hope their findings will prompt the FDA to expand the EUA to include outpatients.

"We have shared this data with both the World Health Organization and the FDA," study co-author Kelly Gebo, MD, MPH, said during the media briefing.

"We do believe that this could be scaled up quickly," added Gebo, professor of medicine at Johns Hopkins University School of Medicine. Convalescent plasma "could be used as a potential treatment as variants continue to evolve, such as we've seen with Omicron."

Pre-Omicron Results

The study was conducted at Johns Hopkins University and 23 other sites nationwide between June 2020 and October 2021. This means researchers enrolled symptomatic adults during circulation of the SARS-CoV-2 ancestral strain and the Alpha and Delta variants.

However, Sullivan said, "We think that...plasma with high levels of antibodies can adapt faster to Omicron, although it will take us longer to get an Omicron-specific supply."

Because of the timing of the study, 80% of participants were unvaccinated. Mean age was 44 years and 57% were women. Black and Hispanic participants each accounted for more than 12% of the study population.

On average, participants received a transfusion within 6 days of the start of symptoms.

In the study, 37 people out of 589 control group participants were hospitalized, compared to 17 of the 592 who received the convalescent plasma.

"We know antibodies work against SARS-CoV-2. The vaccines have been spectacular ― producing antibodies that reduce hospitalizations and prevent transmission," Sullivan said. "Convalescent plasma provides much of the same antibodies instantly."

Convalescent and Controversial

Convalescent plasma has been one of the controversial treatments for people with COVID-19 ― with studies going back and forth on the potential benefits and efficacy. An NIH-funded study published in August 2021, for example, showed no significant benefit.

"As you know, convalescent plasma has had a rocky ride," Casadevall said.

"It was deployed with great excitement in the terrible, early days of the pandemic. Unfortunately, the early excitement and optimism was dampened with some of the randomized control trials appearing to show no benefit in reducing mortality and hospitalized patients," he added.

In contrast, the current study shows "where convalescent plasma works using the latest. most rigorous clinical investigation tools available: a double-blinded, randomized, placebo-control trial," Casadevall said.

Why a Preprint, and Why Now?

The researchers decided to release their data today in recognition of the lag time between reporting of COVID-19 cases and hospitalizations, Sullivan said. "That's part of the reason we decided to act now with this knowledge ― that it does take a couple of weeks ― with cases of Omicron going up."

Furthermore, "We thought this was actionable data for decision-makers," he added.

A reporter asked why the Johns Hopkins researchers chose to hold a media briefing for a preprint study.

A preprint is "not so unusual given the SARS-CoV-2 pandemic," said study senior author Daniel Hanley, MD, division director of brain injury outcomes at Johns Hopkins University School of Medicine.

"The data are the data," Casadevall added. "This is not going to change from peer review."

Peer review may change some of the wording of the manuscript, but not the numbers, he added.

"Now with the Omicron crisis and the fact that we have lost some more main monoclonal antibodies, it is essential to get this information out," Casadevall said.

Plasma Therapy Nothing New

Donation and transfusion of convalescent plasma is highly regulated with strict criteria, said Evan Bloch, MBChB, associate director of the Transfusion Medicine Division at Johns Hopkins University School of Medicine.

If the FDA opts to expand the EUA based on this or other evidence, administration of convalescent plasma could be rolled out fairly quickly, the researchers note.

Plasma transfusion takes place in hospitals and at infusion centers every day. The infrastructure is in place in many countries, even low- and middle-resource nations, around the world to provide convalescent plasma therapy. The major difference between traditional plasma and SARS-CoV-2 convalescent plasma is the indication, Bloch added.

In addition, convalescent plasma has a polyclonal composition ― a benefit compared to monoclonal antibodies, he added. "It's more durable or adaptive [compared to] some of the targeted therapies, such as monoclonal antibodies, where we've witnessed this diminished efficacy with viral evolution."

medRxiv. Published online December 21, 2021. Full text

Damian McNamara is a staff journalist based in Miami. He covers a wide range of medical specialties, including infectious diseases, gastroenterology and neurology. Follow Damian on Twitter: @MedReporter.

For more news, follow Medscape on Facebook, Twitter, Instagram, and YouTube.


Comments on Medscape are moderated and should be professional in tone and on topic. You must declare any conflicts of interest related to your comments and responses. Please see our Commenting Guide for further information. We reserve the right to remove posts at our sole discretion.