The Food and Drug Administration (FDA) will allow plasma donations from survivors of the novel coronavirus to treat coronavirus patients in the absence of an approved vaccine.

New York Gov. Andrew Cuomo (D) announced yesterday that the state health department would begin the treatment, known as convalescent plasma, for the sickest coronavirus patients, echoing an approach used for some victims of the 1918 flu pandemic.

The method was also associated with the lessening of symptoms and shorter hospital stays for SARS patients during the 2002 outbreak, and has shown signs of effectiveness in treating novel coronavirus patients in China, NBC News reports.

“The approach definitely has merit, and what’s remarkable about it is it’s not a new idea; it’s been with us for a good hundred years or longer,” Dr. Jeffrey Henderson, an associate professor of medicine and molecular microbiology at the Washington University School of Medicine in St. Louis, told NBC News.

“I think we don’t know until we have experience and case reports with this particular disease whether it will be effective, but just based on its track record with a number of other viruses, I think it has a very good chance of working,” he added.

The FDA has approved emergency protocols that allow doctors to request permission on a case-by-case basis for coronavirus patients. The plasma treatment will be exclusively used for critically ill patients who are at risk of death, with the FDA responding to most requests within four to eight hours and doctors having the option to contact the FDA’s Office of Emergency Operations for more time-sensitive cases.

The FDA added that the treatment has not yet been definitively proven effective against the coronavirus in general.

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