People who have recovered from COVID-19 may have an outlet to help those ill with the disease caused by the new coronavirus: Donating their plasma.

In Arizona, a blood donation company, Vitalant (formerly United Blood Services), is starting to allow recovered patients to donate as part of a pilot program.

There are no proven treatments for COVID-19 because the virus is new and it can take a long time to find effective treatments. A vaccine for COVID-19 likely is many months, if not more than a year, away, though trials are underway.

Plasma from recovered COVID-19 patients has offered some promise in anecdotal use and in past coronaviruses to treat people, experts say.

"Unfortunately, it's kind of the only ray of hope at present until we identify some medications that have some promise," said Dr. Ralph Vassallo, Vitalant's chief medical and scientific officer.

In New York, which has been badly hit by the virus, hospitals and blood centers are ramping up plasma donations from recovered COVID-19 patients. Some patients have already been infused with this plasma in New York and Houston.

How could plasma help?

When people get sick, the body produces antibodies, which are proteins in the blood that rise up to fight infections as part of an immune response.

These antibodies can remain in the body for quite some time. Once a person has recovered from an infection, their blood contains antibodies that could be helpful in fighting the same infection in another person.

Antibody testing can see if a person shows markers of having had an infection that the body created antibodies to fight against. This kind of testing is not yet widely available to people who believe they may have had COVID-19.

Plasma is the liquid part of the blood that remains after blood cells and platelets are removed. The plasma for this purpose is called "convalescent plasma," which refers to plasma collected from people who have recovered from an infection.

The use of this kind of plasma has been studied for other respiratory infections, such as SARS, MERS and H1N1, the U.S. Food and Drug Administration says on its website.

Using plasma collected from recovered COVID-19 patients is an "investigational treatment" for the disease, according to the FDA. It's possible that plasma from recovered patients has antibodies to the virus that could fight against the virus in other patients.

"Although promising, convalescent plasma has not yet been shown to be effective in COVID-19," the FDA's website says.

Before convalescent plasma can be used routinely to treat COVID-19 patients, clinical trials are needed to show it's safe and effective, the FDA says. The FDA has opened up options for doctors, investigators and universities to use this treatment and study how it's working.

Doctors may use convalescent plasma to treat a patient who has COVID-19 in certain conditions apply and by submitting an emergency investigational new drug application to the FDA, the agency said.

Who's collecting plasma in Arizona?

Vassallo, of Vitalant, said the company is starting pilot programs in Arizona, Colorado, New Mexico and Pennsylvania. In Arizona, the company has partnered with Mayo Clinic, Vassallo said.

"Eventually, we'll likely expand that pilot," Vassallo said. "We've been talking with several other hospitals and they're beginning to prepare on their end what's necessary to participate in these investigational new drug studies."

The details of the program with Mayo Clinic in Arizona are still being worked out, Vassallo said, and the program should be available soon.

Vitalant has started collecting convalescent plasma at sites outside Arizona as of Monday, he said.

Mayo Clinic in Rochester, Minn., announced on Friday that it would lead a clinical trial into the use of convalescent plasma to treat COVID-19.

Mayo Clinic in Arizona said it was premature to discuss the pilot program with Vitalant.

People who have recovered from COVID-19 can access Vitalant's website, and the company will connect them with local clinicians to make sure it's safe for the patient and others to donate at this time, Vassallo said. Vitalant will then draw their plasma and send it back to hospitals where it can be used for investigative use as allowed by the FDA, he said.

Vitalant has released materials to physicians in pilots in those four states and will probably begin collecting plasma Monday, he said.

Prospective donors must have been symptom-free for at least 14 days and test negative for COVID-19.

People also have to have tested positive for COVID-19 at some point. They can't donate only if they believe they have had it, but didn't get testing. And with testing in Arizona being very limited, and the scope of the virus believed to be broader than official numbers suggest, that could cut off many potential donors.

Eventually, Vassallo said, antibody testing will be implemented that will allow health professionals to see if people have previously had COVID-19. That type of testing could then aid plasma donations.

The American Red Cross said it was asked by the FDA to identify donors and manage the distribution of convalescent plasma. It is working to develop a way to identify people who have recovered from COVID-19, the organization said in a statement.

The Red Cross set up a website, RedCrossBlood.org/plasma4covid, where prospective donors can submit their information and get appointments to donate.

Reach reporter Rachel Leingang by email at rachel.leingang@gannett.com or by phone at 602-444-8157, or find her on Twitter and Facebook.

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