The U.S. Food and Drug Administration (FDA) announced the approval of convalescent plasma therapy for patients with coronavirus.

The agency announced the approval on the same day when New York Governor Andrew Cuomo announced the initiation of clinical trials using blood plasma from patients who have recovered from the coronavirus infection.

On Tuesday, the FDA said it would allow doctors to use convalescent plasma that is collected from recovered coronavirus patients in an effort to treat critically ill COVID-19 patients.

The plasma collected from recovered patients contains antibodies against the coronavirus, which will be administered into seriously ill patients.

The FDA said in guidance that this experimental therapy could prove effective against COVID-19, although the evidence is not strong enough to support that as of now.

Convalescent plasma therapy was studied in outbreaks of other respiratory infections, such as the 2003 SARS epidemic, 2009-10 H1N1 flu virus pandemic, and 2012 MERS epidemic.

The U.S. drug regulatory body said, “Although promising, convalescent plasma has not been shown to be effective in every disease studied.”

“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,” it added.

The agency said it is not feasible to obtain access to convalescent plasma therapy in the time of pandemic; however, it would facilitate access to the treatment given the global threat of the coronavirus.

The FDA said it was allowing physicians to use the procedure through “the process of single-patient emergency Investigational New Drug Applications under its authority.”

It has set strict guidelines for the blood to be donated for the use of this therapy. The agency also said that this procedure is not for the prevention of COVID-19.

New York state, which is not the U.S. epicenter of the coronavirus outbreak, has been working with an unnamed drug company on its clinical trial program with convalescent plasma.

Takeda Pharmaceutical, a Japanese multinational pharmaceutical, and biopharmaceutical company, has been working on developing COVID-19 treatment from the blood of patients who have recovered from the infection. The company’s TAK-888 is an anti-COVID-19 polyclonal hyperimmune globulin, which is currently in development to treat patients who are at greater risk.