Liver transplant recipients (LTRs) are highly susceptible to severe COVID-19. This study investigated humoral and cellular immune responses to BNT162b2 or mRNA-1273 vaccines in LTRs and healthy donors (HDs). LTRs showed weaker anti-RBD IgG induction, further reduced by multiple immunosuppressants. CD4⁺ T-cell responses were also limited, but both antibody and CD4⁺ T-cell responses improved with a third vaccination. CD8⁺ T-cell responses were quantitatively, but not qualitatively, reduced in LTRs, with no boosting effect from a third dose. A third mRNA vaccination may be beneficial for LTRs, although further research is needed to optimize CD8⁺ T-cell responses.
