Responses to COVID19 Vaccination in Patients With a Treatment History of Rituximab.

Inclusion Criteria: 1. Patients who were treated with anti-CD20 treatment since 01.01.2010 2. Patients who received a COVID19 vaccination (completion of all required doses) until target date (initial target: 30.05.21, but can be delayed to 30.06.21, 30.07.21 or 30.08.21 in case of insufficient enrollment) 3. Volunteers without a history of anti-CD20 treatment exposure 4. All: written informed consent. Exclusion Criteria: Exclusion criteria for patients (any of the following) 1. Patients aged 18 years and younger at time of study enrollment and/or 2. Pregnant or lactating women at time of study enrollment and/or 3. Patients who do not provide written informed consent and/or 4. Patients who have previously had a COVID19 infection (self-reported COVID19 disease, positive PCR or serology) 5. Patients who are in a dependency relationship with the study personnel (hierarchical, social) Exclusion criteria for volunteers (any of the following) 1. Volunteers aged 18 years and younger at time of study enrollment and/or 2. Pregnant or lactating women at time of study enrollment and/or 3. Volunteers who do not provide informed consent and/or 4. Volunteers who suffer from an active autoimmune disease, active cancer, immunosuppressive therapy, history of anti-CD20 treatment and/or 5. Volunteers who have previously had a COVID19 infection (self-reported COVID19 disease, positive PCR or serology) 6. Volunteers who did not complete their COVID19 vaccination 7. Volunteers who are in a dependency relationship with the study personnel (hierarchical, social)