Immunogenicity and Adverse Effect of Two Dose BNT162b2 mRNA Vaccine Among Liver Transplant Recipients.

BNT162b2 mRNA vaccine against SARS-CoV-2 has been shown to be safe and effective in immunocompetent subjects. The safety and efficacy of this vaccine in liver transplant (LT) recipients is still under evaluation. The objective of this study was to assess the safety and efficacy of BNT162b2 vaccine among transplant recipients. The immune responses of 76 LT recipients receiving two doses of the vaccine were compared to those of 174 age-matched immunocompetent controls. Post-vaccination IgG antibodies against the RBD of SARS-CoV-2 and neutralizing antibodies (NA) to BNT162b2 mRNA vaccine were determined at least 14 days after second dose of vaccine. IgG antibody titers ≥1.1 were defined as positive antibody. Side effects were monitored during study period. Following administration of the second dose, transplant recipients showed reduced immune responses as compared with controls (72% vs. 94.2%, p<0.001). At a median time of 38 days after the second vaccination geometric mean of receptor-binding domain IgG and NA titers were 2.05 (95% CI, 1.6-2.6) and 150.2 (95% CI, 96-234) among transplant recipients and 4.56 (95% CI, 4.1-5.1) and 429 (95% CI, 350-528) in the control group, respectively p<0.001. Antibody responses were lower in transplant recipients who were receiving combined immunosuppression therapy and in those with impaired renal function. Among LT recipients with negative antibody response, one became infected with SARS-CoV-2 and none with positive antibody response did. Overall, most (n=39 [51%]) side effects self-reported by transplant recipients were mild and occurred more often in women than in men. Compared with immunocompetent patients, LT recipients had lower immune response. The durability of immune response to the BNT162b2 vaccine among LT recipients requires further investigation.