US hospitals are gearing up to test a century-old treatment used to fight off flu and measles outbreaks in the days before vaccines and tried more recently against Ebola and severe acute respiratory syndrome (SARS). This treatment might also work for COVID-19.

The US Food and Drug Administration said it is expediting approving the use of recovered patients’ plasma to treat the newly infected.

When a person gets infected by a particular virus, the body starts making specially designed proteins called antibodies to fight the infection. After the person recovers, those antibodies float in survivors’ blood – specifically in the plasma, the liquid part of blood – for months, even years.

Injecting the plasma into another infected patient could boost the body’s ability to fight the infection, lessening the severity of the disease and freeing up hospital resources.

“Every patient that we can keep out of the ICU [intensive care unit] is a huge logistical victory because there are traffic jams in hospitals,” Michael Joyner, an anesthesiologist and physiologist at the Mayo Clinic in Rochester, Minnesota, told Nature scientific journal.

“We need to get this on board as soon as possible, and pray that a surge doesn’t overwhelm places like New York and the West Coast.“

Doctors in China attempted the first COVID-19 treatments using donated plasma from survivors of the new virus, but studies done there have only yielded preliminary results.