Humoral response to 2-dose BNT162b2 mRNA vaccine for Covid-19 in liver transplant recipients

Abstract

Introduction: In the context of the Italian SARS-CoV-2 vaccination program, liver transplant (LT) recipients were prioritized for vaccine administration, although the lower response to vaccines is a well known problem in this population. Aim: We aimed to evaluate immunogenicity of BNT162b2 mRNA vaccine in LT recipients and healthy controls and to identify factors associated with negative response to vaccine. Materials and Methods: We prospectively evaluated a cohort of adult LT patients the humoral response (with anti-Spike protein IgG-LIAISON SARS-CoV-2 S1/S2-IgG chemiluminescent assay) at 1 and 3 months after 2-dose vaccination. A group of 307 vaccinated healthcare workers, matched by age and sex, served as controls. Results: Overall, 492 LT patients were enrolled (75.41% male, median age 64.85 years). Detectable antibodies were observed in the 75% of patients with a median value of 73.9 AU/mL after 3 months from 2-dose vaccination. At multivariable analysis, older age (>40years, p=0.016), shorter time from liver transplantation (<5years, p=0.004), and immunosuppression with antimetabolites (p=0.029) were significantly associated with non-response to vaccination. Moreover, the LT recipients showed antibody titers statistically lower than the control group (103 vs 261 AU/ml, p<0.0001) (fig. 1). Finally, both in controls and LT patients we found a trend of inverse correlation between age and antibody titers (correlation coefficient: -0.2023 and -0.2345, respectively). Conclusions: Three months after vaccination, LT recipients showed humoral response in 75% of cases. Older age, shorter time from transplantation and use of antimetabolites were factors associated with non-response to vaccination and needed to be kept under close monitoring.