* past infection with sars-cov-2 * pregnancy * age below 18 years * active infection additional exclusion criteria for rct only: - recipients at a high risk for acute or chronic humoral rejection including: * recipients with positive panel-reactive antibody (pra) (any positive value) at any time before or after transplantation * recipients that had an acute rejection in the last year * recipients less than 6 months after transplantation * recipients that are considered at high risk for rejection according to the primary care nephrologist * recipients taking less than 3 anti-rejection medications * recipients currently treated with mtor inhibitors (everolimus, sirolimus) and/or azathioprine * recipients treated with plasmapheresis in the previous 3 months * recipients treated with eculizumab in the last year * recipient treated with ivig in the previous 3 months * recipient treated with rituximab in the previous 6 months

* past infection with sars-cov-2 * pregnancy * age below 18 years * active infection additional exclusion criteria for rct only: - recipients at a high risk for acute or chronic humoral rejection including: * recipients with positive panel-reactive antibody (pra) (any positive value) at any time before or after transplantation * recipients that had an acute rejection in the last year * recipients less than 6 months after transplantation * recipients that are considered at high risk for rejection according to the primary care nephrologist * recipients taking less than 3 anti-rejection medications * recipients currently treated with mtor inhibitors (everolimus, sirolimus) and/or azathioprine * recipients treated with plasmapheresis in the previous 3 months * recipients treated with eculizumab in the last year * recipient treated with ivig in the previous 3 months * recipient treated with rituximab in the previous 6 months

past infection with sars-cov-2 pregnancy age below 18 years active infection additional exclusion criteria for rct only: - recipients at a high risk for acute or chronic humoral rejection including: recipients with positive panel-reactive antibody (pra) (any positive value) at any time before or after transplantation recipients that had an acute rejection in the last year recipients less than 6 months after transplantation recipients that are considered at high risk for rejection according to the primary care nephrologist recipients taking less than 3 anti-rejection medications recipients currently treated with mtor inhibitors (everolimus, sirolimus) and/or azathioprine recipients treated with plasmapheresis in the previous 3 months recipients treated with eculizumab in the last year recipient treated with ivig in the previous 3 months recipient treated with rituximab in the previous 6 months

past infection with sars-cov-2 pregnancy age below 18 years active infection additional exclusion criteria for rct only: - recipients at a high risk for acute or chronic humoral rejection including: recipients with positive panel-reactive antibody (pra) (any positive value) at any time before or after transplantation recipients that had an acute rejection in the last year recipients less than 6 months after transplantation recipients that are considered at high risk for rejection according to the primary care nephrologist recipients taking less than 3 anti-rejection medications recipients currently treated with mtor inhibitors (everolimus, sirolimus) and/or azathioprine recipients treated with plasmapheresis in the previous 3 months recipients treated with eculizumab in the last year recipient treated with ivig in the previous 3 months recipient treated with rituximab in the previous 6 months