Background: Immune responses of solid organ transplant recipients to two doses of the BNT162b2 mRNA anti-SARS-CoV-2 vaccine is 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 recipients 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 cells levels before and 21-28 days a third vaccine dose were determined. Adverse effects after the third dose were monitored. Results: The LT recipients were of a median age of 65 years; 57.4% were male. The humoral immune response rate improved significantly, with 56% of patients showing a response before the third vaccine to 98% after the third vaccine. 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 compared to calcineurin inhibitor monotherapy (p=0.001). After the third dose, adverse effects 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 determine the optimal number and schedule of boost vaccines.

Fuente: Journal of Hepatology
Available online 19 April 2022