Plasma, a 19th-century treatment, is being used to battle coronavirus infections

Gravely ill with the coronavirus, Renee Bannister had spent three weeks on a ventilator — a sophisticated electronic device that helped her breathe — before she underwent a treatment that dates to the late 1800s.

The Gloucester County woman was infused with golden fluid called plasma, harvested from her niece, Marisa Leuzzi of Downingtown, who had previously recovered from the virus.

Bannister, 63, got the treatment April 3 and is now out of intensive care at Virtua Voorhees Hospital. She is expected to move to a rehab facility within days, aiming to make it home before her wedding anniversary in late May.

Did her niece’s plasma make the difference?

That is the big unknown for Bannister and hundreds of others who have now undergone similar treatments in the United States, including at least two dozen patients in Pennsylvania and New Jersey. Physicians at Children’s Hospital of Philadelphia, Thomas Jefferson University, Rutgers Health, and the University of Pennsylvania all are on the case.

At its core, the idea is as simple as it is elegant: After individuals have recovered from the coronavirus, their plasma (the liquid component of blood) still contains antibodies that the immune system developed to fight off the disease.

This antibody-laden plasma can be donated and administered to others who have not yet recovered. More than a century ago, such treatments were used against measles and other infectious diseases before vaccines were available.

Small studies from China have found that some patients with the coronavirus improve after getting the treatment, said Emma Meagher, chief clinical research officer at Penn’s Perelman School of Medicine. But clinical trials are needed to determine if they would have gotten better on their own, or if other approaches might have been better.

“There is really very limited information on whether this works,” she said.

Bannister’s husband, Greg, has little doubt.

“We are relieved and overjoyed,” he said in a news release from Virtua.

Leuzzi, the couple’s niece, donated enough plasma at a nearby Red Cross facility to help two Virtua patients.

The second was Mount Laurel resident Andy Fei, 61, an opera singer who had been on a ventilator for six days when he received the plasma April 5. He was well enough to be disconnected from the ventilator nine days later, though he remains in the hospital, Virtua said.

As with plasma donated for other conditions, the fluid is tested to ensure the blood types are compatible, and to make sure it does not contain viruses such as hepatitis.

Donors also must document that they tested positive for the coronavirus and that they subsequently tested negative. (Those who are symptom-free for four weeks generally do not need that second test, though requirements differ slightly at various sites.)

But the donor’s level of antibodies is not measured, as such tests have not yet been validated, said Kristen Rising, one of the physicians overseeing plasma treatment for the Jefferson health system.

Another unknown is when it might be best to administer the treatment, she said. Donor antibodies might be more useful earlier in the course of the disease, when patients’ immune systems have yet to make their own. But physicians are reluctant to use unproven treatments on people who are likely to recover without them, as any medical procedure involves some degree of risk.

» READ MORE: How to donate plasma

On the other hand, if physicians wait until a person has severe symptoms from the coronavirus, the bigger challenge might not be fighting the virus itself but inflammatory damage from an overactive immune system. Rising said she and her colleagues are targeting patients whose vital signs suggest they are at risk of decline.

At CHOP, where one patient has been treated with plasma yet remains critically ill, physician David Teachey agreed that timing is crucial.

“A lot of times, for the patients who are critically ill in the ICU, even getting rid of the virus isn’t going to fix things,” said Teachey, an oncologist who studies “dysregulation” of the immune system.

At Penn, physicians plan to study response to plasma in two formal clinical trials, overseen by Katharine Bar, an assistant professor of infectious diseases. Both involve patients who are hospitalized with the coronavirus, one with those who are in intensive care, the other not.

In New Jersey, Rutgers physicians have treated 17 patients with plasma at University Hospital in Newark. Nationwide, hundreds of others have been treated with plasma donated to the American Red Cross, said David Moolten, medical director for blood services in the Pennsylvania-New Jersey region.

People who have recovered from the coronavirus can register with these sites to see if they are eligible to donate plasma: