Introduction: Some previous research suggests that a protective immune response after vaccination is diminished in kidney transplant recipients. The literature in other types of solid organ transplant is even scarcer. With the development of the SARS-CoV-2 vaccines, there was fear that transplant recipients would not mount a sufficient response to vaccination. We sought to evaluate the antibody response of liver transplant recipients to SARS-CoV-2 vaccination, especially in liver transplant recipients. Various guidelines suggest transplant recipients should be vaccinated, and are eligible for additional doses in cases with an inadequate response.

Methods: During routine follow up of 262 liver transplant recipients (earliest date of transplant 1998) at Universitätsklinikum Graz we gathered the information about their vaccination status. As part of routine follow up, we also determined the serum concentrations of SARS-CoV-2 antibodies.

Results: Of the 262 patients in follow up, we currently have the vaccination details of 128 who received at least one vaccine dose. 2 patients received an initial two doses of a vector vaccine, all other doses were of an mRNA vaccine. Of the 127 patients who were vaccinated at least twice, 107 achieved an excellent response (>100U/mL) and 7 achieved an adequate response (>=30U/mL). Of the 13 patients who achieved an inadequate response (<30U/mL), 6 had no detectable circulating antibodies. Of the 115 patients who were vaccinated at least three times, 101 achieved an excellent response and a further 6 adequate. 8 patients still did not achieve an adequate response (of which 2 had no response).

Conclusion: After at least two vaccine doses, 89.8% (114/127) of patients had an adequate response to the vaccine. After the third dose, the response rate rose slightly to 93.0% (107/115). The currently available vaccines appear to provoke a sufficient antibody response in liver transplant recipients.