When most people recover from a viral infection, they'll have antibodies in their blood.
Antibodies tightly bind to viruses and help clear them from your bloodstream; they're part of your immune system.
Officials with Geisinger Health System say antibodies were helpful in treating people during the SARS epidemic, and SARS is another type of coronavirus.
So they're recruiting COVID-19 survivors to donate their blood plasma to others currently fighting the virus.
It's called convalescent plasma, and the thought is that it can help someone else's immune system.
We spoke with Dr. Gustaaf De Ridder, Geisinger's system director of transfusion services.
Geisinger has been giving convalescent plasma to patients for a few weeks.
"People started trying giving one person's plasma to another sick person, over a hundred years ago," said Dr. De Ridder. "We can't say that this works well. This is an educational treatment, just like anything else we're using to combat this virus."
Dr. De Ridder says they've received hundreds of phone calls per day, people who think they had coronavirus, offering to donate.
He wants to stress you can only be a donor if you were officially diagnosed with COVID-19 and have been symptom-free for 28 days, or if you were diagnosed with COVID-19, have been symptom-free for 14 days, and have since had a negative follow-up test.