At Wednesday’s White House task force briefing, Anthony S. Fauci addressed the theory that antibodies can be transferred from a person who has recovered to a person who is still fighting the illness, to help bolster their immune systems.

“This is an old concept," Fauci said. "In fact, immunology was born decades and decades and decades ago with the concept of giving passive transfer of serum to an individual to protect them from an infection.”

Infusions of antibody-rich plasma — the clear liquid that remains when blood cells are removed — may help a sick person’s immune system fight off the illness. The same concept was successful against polio, measles, mumps and flu.

Doctors and researchers are hopeful that a “convalescent plasma” treatment will help provide short-term relief to the health-care system and its patients while scientists develop a long-lasting vaccine — something that could take more than a year — or full antibody therapies, which drug companies are also working on.

Fauci said he wouldn’t be surprised if a number of researchers are pursuing the treatment. “It’s the right thing to do,” he said.

Whether developing an antibody test should be the priority right now is a different matter. Fauci said developing such a test is the right goal, but that it wasn’t something that should be prioritized over testing for the infection and a vaccine.

“Right now, that's not our immediate problem,” Fauci said.

Task force coordinator Deborah Birx said she’s focused on getting a simple screening test for the infection, particularly for health-care workers who are putting their lives on the line every day. But she said she’s also encouraging researchers and scientists to work on the antibody test.