(651) Long-Term Safety and Efficacy of Mrna Sars-Cov2 Vaccination in Heart Transplant Recipients

PURPOSE: Data on long-term clinical effects of mRNA SARS-CoV2 vaccination in heart transplant recipients are scarce and conflicting. We investigated the long-term safety and efficacy of mRNA SARS-CoV2 vaccination in this patient population. METHODS: In a prospective single-center cohort study we included 54 consecutive adult heart transplant recipients who received 2 doses of mRNA SARS-CoV2 vaccine between January 1 and June 30, 2021. 3 months after the 2(nd) dose, an assessment of humoral (total antibody levels to the receptor-binding domain of SARS-CoV2 spike (S) protein using anti-RBD immunoassay) and cellular (IFN-γ response to S-peptide stimulation of recipient T lymphocyte populations) response to vaccination was assesed. Subsequent booster vaccination was done per patients' preference between 3 and 6 months after initial vaccination. All patients were followed every three months for 12 months after inital vaccination. RESULTS: Of 54 recipients, 44 (81%) were male with a mean age of 63±8 years and a mean time from transplantation of 6.6±4.0 years. Immunosupressive regimen consisted of tacrolimus (mean C0 level 7.4±1.7 μg/mL), mycophenolate mofetil (mean dose 2120±419 mg) and steroids (mean dose 2.5±0.9 mg). 83% of patients received BTN162b2, and 17% mRNA-1273 vaccine. At 3 months, any humoral response was present in 24 (44%) of the recipients (median anti-S serum level 35.5 BAU/mL), and cellular response was present in 3 (6%) recipients. No simultaneous humoral and cellular responses were observed. During follow-up, 35 recipients (Group A) received a booster vaccine and 19 recipients (Group B) did not. While the two groups did not differ in clinical, transplant and immunosuppression parameters, patients in Group A were less likely to develop Covid-19 infection (31% vs. 67%; P=0.01). Importantly, the need for hospital admission due to Covid-19 (20% vs. 33%; P=0.39) did not differ between the two groups. In 3 (6%) recipients we found worsening of allograft function, occurring within 1 month after the second vaccination dose. CONCLUSION: Long-term effects of mRNA SARS-CoV2 vaccination in heart transplant recipients appear to be less pronounced than in general population with modest additional clinical benefit of booster vaccination. While generally well-tollerated, mRNA SARS-CoV2 vaccination may also be associated with worsening of allograft function.