Doctors are hopeful that plasma therapy could be a successful treatment option for patients with coronavirus (COVID-19).

The treatment uses blood samples taken from people who have recovered from the virus and injects them into people currently fighting it to help provide antibodies.

The practice has been recently used to treat Ebola, SARS (another strain of coronavirus) and H1N1 flu patients.

The experimental practice was used during the devastating 1918 flu, as well as to treat measles in the 1930s. In recent years, plasma therapy been used to treat victims of Ebola, SARS and H1N1 influenza. The method was also used in combatting the influenza pandemic of 1918.

Since the Food and Drug Administration authorized the emergency use of plasma transfusion for individual patients who are critically ill with COVID-19, a few hospitals have begun to implement the practice.

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Baptist Health Lexington in Kentucky has performed transfusions on two critically ill patients since obtaining permission from the FDA.

“In an attempt to help our more critically ill COVID-19 patients we initiated an investigational compassionate plea FDA protocol using convalescent plasma therapy,” Dr. Mark Dougherty, infectious disease specialist and hospital epidemiologist, said in a statement.

There have been no large-scale studies of the practice, but a small study of 10 patients resulted in “clinical improvement, no deaths, improved lung findings.”

Dr. Robert Kruse, a resident at John Hopkins Medicine, noted that the study suggested collecting samples from patients “as soon as they recover.”

“Antibody levels may decrease over next few months, so get them while high. Given urgency of outbreak, [people] were likely to do so anyways,” Kruse tweeted.

Dozens of blood centers nationwide have begun collecting plasma samples for the therapy, after AABB, an international nonprofit agency focused on transfusion medicine and cellular therapies, issued guidelines Tuesday permitting local blood centers to collect recovered COVID-19 patients’ samples.

“There isn’t anything else out there,” Dr. Louis Katz, a blood industry expert who is leading the AABB’s working group on plasma therapy, told NBC. “There are historical precedents that it may be beneficial and enough early data that it’s safe.”