Live-attenuated vaccine failure after liver transplantation: A 20-year cohort study

Background: A recent conditional recommendation suggests considering live-attenuated vaccines for solid organ transplant recipients, yet the conditions of their safe and effective administration remain unclear. Methods: This prospective study was conducted at Keio University Hospital from 2002 to August 2023. We gave a live-attenuated vaccine to liver transplant (LT) recipients fulfilling criteria for live-attenuated vaccines, including criteria for humoral and cell-mediated immunity. Patient background information, immunization date, vaccine strain, immunosuppressive agents at the time of vaccination, and antibody titers were collected. Factors related to primary and secondary vaccine failure were evaluated to enhance the effectiveness of the live-attenuated vaccine program after LT. Results: Among 67 LT recipients, 54, 55, 47, and 55 received at least one dose of live-attenuated vaccine for measles, rubella, varicella, and mumps, respectively. The difference in vaccine strains, but not the use of two or more immunosuppressive agents, was associated with a lower risk of vaccine failures. Measles vaccine with the AIK-C strain exhibited significantly lower primary and secondary failure rates than the CAM-70 strain (1/38 vs. 4/16, odds ratio: 0.08, 95 % confidence interval [CI]: 0.01–0.80, p = 0.02, and hazard ratio: 0.54, 95 % CI: 0.34–0.85, p = 0.01, respectively). No primary failures were observed with the TO-336 strain of rubella, whereas 4 of 10 LT recipients with the Matsuura strain of rubella did not seroconvert. For mumps, the Hoshino strain showed lower primary failure rates than the Torii strain (15/52 vs. 3/3, p = 0.03). Conclusion: According to a 20-year long-term study, vaccine strains are the most critical factor influencing primary and secondary vaccine failure in post-transplant live-attenuated vaccination.