Mycophenolate mofetil decreases humoral responses to three doses of SARS-CoV-2 vaccine in liver transplant recipients

Background and Aims After 2 doses, the efficacy of anti-SARS-CoV-2 vaccination seems to be lower in solid organ transplant recipients than in the immunocompetent population. The objective of this study was to determine the humoral response rate after vaccination, including with a booster dose, and to identify risk factors for non-responsiveness in liver transplant recipients. Methods We included all patients seen in consultation in two French liver transplant centres between January 1, 2021, and March 15, 2021. Results 598 liver transplant recipients were enrolled and 327 were included for analysis. Sixteen patients received one dose, 63 patients two doses and 248 patients three doses. Anti-SARS-Cov-2 antibodies were detected in 242 out of 327 (74.0%) liver transplant patients after vaccination. Considering an optimal serologic response defined as an antibody titre >260 BAU/ml, 172 patients (52.6%) were responders. Mycophenolate mofetil (MMF) treatment was an independent risk factor for a failure to develop anti-SARS-CoV-2 antibodies after vaccination (OR 0.458; 95%CI 0.258-0.813; p = .008). Conversely, male gender (OR 2.247, 95%CI 1.194-4.227; p = .012) and receiving an mRNA vaccine (vs a non-mRNA vaccine) (OR 4.107, 95%CI 1.145-14.731; p = .030) were independent predictive factors for developing an optimal humoral response after vaccination. None of the patients who received the vaccine experienced any serious adverse events. Conclusions Even after a third booster dose, response rate to vaccination is decreased in liver transplant recipients. MMF appears to be a major determinant of seroconversion and optimal response to vaccination in these patients.