A third dose of the BNT162b2 mRNA vaccine significantly improves immune responses among liver transplant recipients

Background & Aims: Immune responses of solid organ trans-plant recipients to 2 doses of the BNT162b2 mRNA anti-SARS-CoV-2 vaccine are impaired. The immunogenicity and safety of a third dose among liver transplant (LT) recipients are unknown. This work aimed to evaluate the immune response of LT re-cipients to a third dose of the BNT162b2 mRNA vaccine.Methods: Consecutive LT recipients (n = 61) in follow-up at Sheba Medical Center were included. Receptor binding domain (RBD) IgG, neutralizing antibody (NA) titers, and T-cell levels before and 21-28 days after a third vaccine dose were deter-mined. Adverse effects after the third dose were monitored.Results: The median age of LT recipients was 65 years and 57.4% were male. The humoral immune response rate improved significantly, with 56% of patients showing a response before the third vaccine dose compared to 98% after the third dose. The cellular response in 12 evaluated patients improved significantly (p = 0.008). The geometric mean of anti-RBD IgG levels, NA levels, and T-cell count also increased significantly after the third dose. NA titers after the third dose negatively correlated with age (p = 0.03), mycophenolate mofetil treatment (p = 0.005), and combined immunosuppression as opposed to calcineurin inhib-itor monotherapy (p = 0.001). After the third dose, adverse ef-fects were reported by 37% of recipients and were mostly mild (local pain and fatigue).Conclusion: After a third BNT162b2 mRNA vaccine, the immune response improved significantly among LT recipients, without serious adverse effects. Further studies are needed to evaluate immune response durability and to determine the optimal number and schedule of booster vaccine doses.Lay summary: The Pfizer-Biotech BNT162b2SARS-CoV-2 vaccine induced significant immunity among liver transplant recipients after a third dose. The majority of the patients developed suffi- cient levels of both humoral and cellular immune responses. Factors that predict non-response were older age and immuno-suppressive medications. (c) 2022 European Association for the Study of the Liver. Published by Elsevier B.V. All rights reserved.

Automated summary

Liver transplant recipients showed significantly improved immune response after receiving a third dose of the BNT162b2 mRNA vaccine. The majority of patients developed sufficient humoral and cellular immune responses. Older age and immunosuppressive medications were predictive factors for non-response.