Infections with Corona-Viruses have shown to be a menace for patients with comorbidities such as hypertension, diabetes, cardiovascular disease or immunosuppression. Those are features almost every nephrological patient brings along, especially those on maintenance dialysis and those with renal transplant. Since the emergence of the novel coronavirus SARS-CoV-2 in November 2019 in Mainland China the fear for pandemic infections has increased. But not only is the course of infection itself important, the prevention of transmission to and by attending medical personnel should be put into perspective. Thus there is a lack of sufficient data of occult immunization or persistent state on immunization. In our study up to 400 health care personnel will be screened serologically for IgM, IgA and IgG against the SARS-CoV-2 virus. Blood and urine samples throughout 12 months will be sampled and analyzed. The aim of the study is to identify the rate of occult immunization and at the same time to gather data about the persistence of immune response to an infection with SARS-CoV-02. The results will help provide sufficient safety measures for health care providers and renal patients undergoing unavoidable clinical treatment.