As health care providers were finding some medicines ineffective in treating COVID-19, they turned to a method long used in treating viruses: convalescent plasma.“In the early days of the pandemic, blood providers everywhere in the U.S. were collecting plasma from people who had a COVID-19 infection and recovered because the plasma actually contains antibodies to COVID itself,” said Kirby Winn, spokesperson for the Mississippi Valley Regional Blood Center.Plasma is the liquid portion of your blood that contains antibodies that fight off infections.Donating plasma is different from donating blood.