A California doctor may have discovered a tool in the fight against the coronavirus: treating patients with the plasma of Covid-19 survivors.

Dr Timothy Byun, Director of St Joseph Hospital in Orange County, California, said a patient who had survived their bout with the virus agreed to donate plasma to the hospital, which the doctors then used to treat a seriously ill patient.

“We happened to find a plasma from a recovered person who was willing to donate,” he told Fox News on Friday. “[The sick patient] has gotten a little bit healthier in terms of his oxygenation setting. He was able to get off the vasopressor medication to increase the blood pressure. He was able to stop that. But it’s really too early to tell whether this treatment has been working.”

Mr Byun said prior to the plasma, his patient had tried drugs like hydroxychloroquine, azithromycin and tocilizumab, but there were no noticeable improvements in the person’s health.

Though it will take time before the doctors can say with confidence that this method of treatment is effective, Mr Byun said that similar treatments were used during the 1918 flu pandemic.

“We don’t have a whole lot of data [showing] whether it’s going to work in this particular virus,” Mr Byun said. “Most recently, Chinese doctors have reported increasing outcomes in a small group of patients... Houston Methodist Hospital, as well as a couple of other hospitals in New York, tried this.”

Washington University in St Louis, Missouri, is also using plasma from formerly infected individuals to treat patients. The university received clearance from the US Food and Drug Administration to test plasma treatment.

The St Louis Business Journal reported that university researchers were using “convalescent plasma” — blood from survivors with antibodies in their blood — to treat critically ill patients, not unlike what Mr Byun was doing in Orange County.

“This is a stone-age approach for the modern age,” Dr Jeffery Henderson, a researcher at the university’s School of Medicine, told the Business Journal. “The immune system of somebody who’s already seen the disease can be used to give an assist to somebody who hasn’t yet seen the disease.”