Case I: As the person's own immune cells produced antibodies against the virus, it is a type of natural active immunity. Case II: Plasma therapy (convalescent plasma) involves transfusion of antibodies from someone who has recovered from COVID-19 (convalescent coronavirus patient) into a critical patient. The therapy is based on the principle that the blood of a recovered patient is rich in antibodies needed to combat COVID-19. So, it is a type of artificial passive immunity.