Immunogenicity and Adverse Effects of the 2‐Dose BNT162b2 Messenger RNA Vaccine Among Liver Transplantation Recipients

The BNT162b2 messenger RNA (mRNA) vaccine against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has been shown to be safe and effective in immunocompetent patients. The safety and efficacy of this vaccine in liver transplantation (LT) recipients is still under evaluation. The objective of this study was to assess the safety and efficacy of the BNT162b2 vaccine among transplant recipients. The immune responses of 76 LT recipients receiving 2 doses of the vaccine were compared with those of 174 age-matched immunocompetent controls. Postvaccination immunoglobulin G (IgG) antibodies against the receptor-binding domain (RBD) of SARS-CoV-2 and neutralizing antibodies (NA) to the BNT162b2 mRNA vaccine were determined at least 14 days after the second dose of the vaccine. IgG antibody titers ≥1.1 were defined as positive antibodies. Adverse effects were monitored during the study period. Following administration of the second dose, transplant recipients showed reduced immune responses compared with controls (72% versus 94.2%; P < 0.001). At a median time of 38 days after the second vaccination, the geometric mean of RBD IgG and NA titers were 2.1 (95% confidence interval CI, 1.6-2.6) and 150 (95% CI, 96-234) among transplant recipients and 4.6 (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 the LT recipients with negative antibody responses, 1 became infected with SARS-CoV-2, but no recipients with positive antibody responses became infected. Overall, most (n = 39 51%) adverse effects self-reported by transplant recipients were mild and occurred more often in women than in men. Compared with patients who were immunocompetent, LT recipients had lower immune responses. The durability of immune responses to the BNT162b2 vaccine among LT recipients requires further investigation.