To investigate short- (3 and 8 weeks) and long-term (6, 9, 12, and 18 months) immune protection or response at the humoral and cellular levels before and after SARS-CoV-2 infection or vaccination in patients with moderately reduced immune status (dialysis patients) and severely reduced immune status (organ transplant recipients, mostly kidney transplant recipients) and immunocompetent subjects (medical staff) in Saxony, Germany.