Inclusion Criteria:  Study population for the cross-sectional study (patients with previous SARS-CoV-2 infection of previous vaccination, evaluation of willingness to get vaccinated:  Patients with solid tumors/haematooncologic diseases regardless of stage that seek treatment in the outpatient clinic of the department of radiooncology from April to September 2021 who will undergo active treatment. Age: 18-120 years Patients that undergo radiotherapy, radio-chemotherapy, radio-hormonotherapy or radio-immunotherapy during the investigation period.  Longitudinal study:  Patients that have not yet received SARS-CoV-2 vaccination, but are scheduled to get the first dose during or up to six weeks after active therapy. Age: 18-120 years  Exclusion Criteria:  Lack of written consent Patients, that are mentally or physically incapable of completing a questionnaire Age: < 18 years A previous SARS-CoV-2 infection is no exclusion criteria!