Mycophenolate has been identified as risk factor for non-response to SARS-CoV-2 vaccination in kidney transplant recipients. Safety and efficacy of temporarily stopping of mycophenolate (or azathioprine) to increase vaccine response has not been established.

This is a non-randomized, controlled pilot study including up to 40 kidney transplant recipients not responding to at least three previous SARS-CoV-2 vaccine doses. Mycophenolate or azathioprine will be stopped for two weeks peri-vaccination starting one week before vaccination until one week after vaccination. Allocation to mycophenoalte or azathioprine discontinuation arm will be based on an overall risk assessment by the transplant physician and patient preference. Patients not stopping mycophenolate or azathioprine will serve as control group.

Inclusion Criteria:

• Patient has received a kidney transplantation
• > 18 years of age
• No SARS-CoV-2 spike protein antibodies four weeks after at least three previous vaccine doses
• Maintenance immunosuppression with mycophenolate or azathioprine

Exclusion Criteria:

• acute illness with fever
• Prior documented infection with SARS-CoV-2
• triple anticoagulation therapy
• Subject is currently enrolled in or has not yet completed at least 30 days since ending other investigational device or drug trial(s), or subject is receiving other investigational agent(s)
• Subject has known sensitivity or intolerance to any of the products to be administered for the purpose of this study
• Subject has any kind of disorder that compromises the ability of the subject to give written informed consent and/or to comply with the study procedures
• Subject is pregnant or breast feeding
• SARS-CoV-2 spike protein antibodies four weeks after the 3rd last vaccination > 0.8 BAU/mL