ABSTRACT
Background Liver transplant (LT) recipients frequently show no or low response after two SARS-CoV-2 vaccinations. However, the relevance of different clinical risk factors (RF) for a suboptimal response is still unanswered. Methods Anti-SARS-CoV-2 antibody titers of 141 LT patients determined after the second vaccination assigned them to low ( < 100 BAU/ml) or high response. The relevance of previously identified clinical RF for low response (diabetes, chronic kidney injury, hypertension or age > 65y) and antiproliferative immunosuppression were now analyzed in detail. Results The full clinical data set was available in 101 patients (55 low, 46 high responders). In total, 82 % of low and 52 % of high responders had one or more clinical RF. The risk of low response for patients having at least one, two or three clinical RF increased from 31 % (N = 10 of 32) to 65 % (N = 45 of 69), 86 % (N = 32 of 37) and 93 % (N = 13 of 14), respectively. If all four RF were present, the risk of low response increased to 100 % (N = 6 of 6). Also, a more frequent use of MMF or mTOR-inhibitors was detected in low responders (74 %) compared to high responders (37 %). Of the 26 % (N = 12) of low responders not receiving antiproliferative immunosuppression the majority had one (25 %) or more (50 %) clinical RF. Conclusion If clinical RF are present, the risk of low SARS-CoV-2 vaccination response increases 1.6-fold and with the number of RF. These data can help to identify patients under immunosuppression with the highest risk of suboptimal response to further SARS-CoV-2 vaccinations.