Liver transplant recipients (n = 61) showed improved humoral immune response after a third BNT162b2 mRNA vaccine against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) (P < 0.0001). The activated T cell counts and the levels of anti-RBD IgG and neutralizing antibodies were increased after the third dose (P = 0.008, P < 0.0001 and P < 0.0001, respectively). Adverse effects, reported by 37% of recipients, were mild.