Plasma is the liquid part of blood. Convalescent plasma means plasma that comes from people who have recovered from an infection, like the coronavirus that causes COVID-19. This plasma may contain antibodies against the virus. Antibodies are proteins that your immune system makes after you have had an infection, that can neutralize or kill the virus and help you to recover. Convalescent plasma may be a treatment option for patients with COVID-19. (source: National Institute Health)