As the novel coronavirus has run rampant, so too have unsupported claims about how to treat it. However, a technique that is more than a century old has shown real promise: plasma therapy.

Plasma therapy came to Jonathan Gerber’s mind when he was treating a man who was ill with COVID-19 and in particularly bad shape.

“The patient was critically ill, requiring a breathing tube and mechanical ventilator to keep him alive,” said Gerber, who is Chief of Hematology-Oncology at UMass Memorial Medical Center in Worcester.

Gerber usually focuses on cancer patients, but lately he’s been spending much of his time on patients battling the coronavirus. This particular patient was having issues with his blood pressure, and sometimes he needed to be paralyzed to relax his chest and let the ventilator work.

“His lungs were really in rough shape,” Gerber said.

Gerber thought plasma therapy might be the patient’s only option.

“One of the oldest therapies we have to treat infectious disease is the transfer of plasma from convalescent people,” said Galit Alter, professor of medicine at the Ragon Institute of Mass. General Hospital, MIT and Harvard. “It’s wild; we’ve been doing this forever.”

The idea is simple. Take someone who has recovered from COVID-19 and have them donate blood. When the lab spins that blood, the cells go to the bottom.

“All the stuff floating on top, that's plasma. Plasma is composed of lots of amazing things,” said Alter. “It's composed of antibodies. It’s composed of all kinds of other molecules that can help to arm cells or educate cells or even temper cells.”

Doctors take that plasma and put it in someone who is currently sick from the novel coronavirus.

In the past, this has been used for diseases like diphtheria, polio, measles and mumps. Clinicians have even infected horses and cows to have them produce the serum. It’s not always a success, but it often produces promising results.

“Individuals who hadn’t recovered essentially completely turned around their clinical course, which was totally magical,” said Alter.

Despite its clinical potential, the treatment still faces logistical hurdles. At UMass, Gerber had to first get federal permission, and then he needed to find a plasma donor with a matching blood type. But he eventually got the plasma and, within a few hours, he said, he saw the patient start to improve.

“[The patient is] by no means out of the woods yet, but [he has] a real fighting chance at this point,” said Gerber.

In the past few days, Gerber has been able to give plasma therapy to several other patients as well.

“It’s honestly better than I expected,” he said. “I would say, [I am] still cautiously optimistic, but very, very optimistic.”

But, he warned, patients and policymakers shouldn’t assume plasma therapy can easily be rolled out on a large scale.

“We are obviously limited by supply and other bottle necks,” Gerber said.

Recovered patients can donate plasma only about every two months. Plus, he said, that plasma varies from donor to donor and the reaction varies from patient to patient. And, Gerber added, it’s not cheap. It costs about $1,000 per transfusion.

Despite these challenges, Galit Alter said studies testing plasma therapy for the novel coronavirus are beginning to happen around the country and the world. There’s a lot of variation between the trials, she said. Some doctors might try it when patients have just fallen ill; others might do the transfusion when things are already severe.

Alter said one type of plasma transfusion involves pooling antibodies from thousands of people who have not had the particular virus that’s being treated. The idea is that those antibodies might reduce a patient’s inflammation to give their system a bit of a break. Then, the patient’s immune system can “go back in and start doing its job properly to control and clear the pathogen from the system,” Alter said.

Plasma therapy won’t just help individual patients who receive the transfusion, Alter said. What we learn from all the plasma studies will also help make better therapeutics and better vaccines.