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Among the myriad clinical trials for vaccines to prevent COVID-19 and drugs to treat infections, doctors are looking to survivors’ plasma for a possible therapy. The US Food and Drug Administration (FDA) released a statement on Tuesday (March 24) stating that investigators can request to use plasma from COVID-19 survivors to deliver antibodies to seriously ill patients, under an emergency investigational new drug (IND) protocol.

Convalescent plasma treatment, as it is known, has roots stretching back over 100 years. It is based on the premise that because a survivor developed antibodies throughout the course of their own infection, blood donations to those who became recently ill would give the recipients’ immune systems a leg up, reducing the severity of the disease and increasing the likelihood of survival. During the 1918 Spanish flu pandemic, the rate of mortality decreased by as much as 50 percent among the patients who received the convalescent treatment, according to a meta-analysis of medical records available at that time and published in the Annals of Internal Medicine in 2006.

To bring the treatment up to modern standards, plasma donations from people who have recovered from COVID-19 infection would be processed and purified, creating a serum to transfuse into critically ill patients.

“Deployment of this option requires no research or development,” Arturo Casadevall, an immunologist at Johns Hopkins Bloomberg School of Public Health, says in a statement. “It could be deployed within a couple of weeks since it relies on standard blood-banking practices.”

In January, Casadevall and Liise-anne Pirofski of New York’s Montefiore Health System wrote in the Journal of Clinical Investigation that convalescent therapy could be used to curb COVID-19. They note that attempts to use convalescent therapies during outbreaks over the last 25 years, including the H1N1 pandemic in 2009 and 2013 Ebola epidemic, were met with varying levels of success, possibly due to the plasma being administered when the patient was too far gone for it to help. Casadevall’s team recently received funding from Johns Hopkins, with a goal of performing these convalescent transfusions at the university’s Baltimore campus within a month.

While an eventual vaccine would ideally provide long-lasting immunity by spurring the recipient to create their own antibodies, receiving antibodies via the convalescent treatment would only form a temporary immunity, so multiple treatments would be required over the course of the illness, according to the Associated Press.

“It must be given at the right time because it mops up the virus in the system and it just gives the new patient’s immune system a vital push at the time it needs it—but it has to be carefully time[d] and it’s not always successful,” Mike Ryan, head of the World Health Organization’s emergencies program, tells STAT.

There are still details that need to be figured out in using convalescent plasma for COVID-19 treatment, including determining an effective dosing size. In its statement announcing the emergency IND access protocols, the FDA outlined standards for donor and recipient eligibility.

“Although promising,” the statement reads, “convalescent plasma has not been shown to be effective in every disease studied. It is therefore important to determine through clinical trials, before routinely administering convalescent plasma to patients with COVID-19, that it is safe and effective to do so.”

Proponents of the treatment have said that it could be very helpful to doctors and nurses on the frontlines, who face repeated exposure and whose absence from work would greatly affect public health, in addition to those who work in nursing homes, caring for people who are most at-risk of experiencing lethal complications from the infection.

“We need to be able to break the cycle of transmission and we also need to be able to help people who are ill,” Pirofski tells the Associated Press.

Plasma transfusions are commonplace nowadays, with patients receiving millions of donated units every year, but they are not without risks. Severe lung injury or allergic reactions can occur after receiving donor plasma.

To achieve similar results to transferring plasma with potentially fewer downsides, some biotech companies are developing antibodies to combat SARS-CoV-2. Vir Biotechnology in San Francisco is focusing its efforts on one particular antibody, STAT reports, though they have developed modifications to make the antibodies to last longer in the body. Vir reports that its drug might be ready for clinical trials as soon as this summer. If those go well, a treatment might be available in the fall.

Lisa Winter is the social media editor for The Scientist. Email her at lwinter@the-scientist.com or connect on Twitter @Lisa831.