SILVER SPRING, MD — The FDA has unlocked the use of convalescent plasma, derived from the blood of people who have recovered from COVID-19 and which may contain helpful antibodies, as an investigational treatment for patients with severe cases of the disease, according to a report from the website FierceBiotech.

This technique has been utilized to treat infectious diseases for decades with the goal of transferring newly acquired immunity from one person to another. It has also been studied in the H1N1 swine flu, ebola, SARS and MERS, as well as against the coronavirus in China.

It is not known how well it will perform in the current form of the coronavirus, however.

“Although promising, convalescent plasma has not been shown to be effective in every disease studied,” the FDA said in an announcement.

“It is therefore important to determine through clinical trials, before routinely administering convalescent plasma to patients with COVID-19, that it is safe and effective to do so.”

Large-scale clinical testing might not be feasible for evaluating this specific and scarce donated plasma, but it would allow physicians to proceed on a case-by-case basis for patients with serious or life-threatening infections outside of larger research studies.

Donors must have had a COVID-19 diagnosis confirmed by a lab test and been completely symptom-free for at least two weeks before donating.

Physicians can obtain authorization over email or receive verbal, over-the-phone confirmations in emergency and time-sensitive cases.

The FDA is also working with the National Institutes of Health and the Centers for Disease Control and Prevention to develop larger protocols for use by multiple researchers to coordinate the collection and use of COVID-19 plasma.

New York Governor Andrew Cuomo said this week that the state department of health would be conducting its own trial of convalescent plasma. As of March 24, New York has more than 30,000 cases statewide, which is nearly half of the 69,000-plus reported in the U.S. as of Thursday afternoon.