Among heart transplant (HT) recipients, a reduced immunological response to SARS-CoV-2 vaccination has been reported. We aimed to assess the humoral and T-cell response to SARS-CoV-2 vaccination in HT recipients to understand determinants of immunogenicity. HT recipients were prospectively enrolled from January 2021 until March 2022. Anti-SARS-CoV-2-Spike IgG levels were quantified after two and three doses of a SARS-CoV-2 vaccine (BNT162b2, mRNA1273, or AZD1222). Spike-specific T-cell responses were assessed using flow cytometry. Ninety-one patients were included in the study (69% male, median age 55 years, median time from HT to first vaccination 6.1 years). Seroconversion rates were 34% after two and 63% after three doses. Older patient age (p = 0.003) and shorter time since HT (p = 0.001) were associated with lower antibody concentrations after three vaccinations. There were no associations between vaccine types or immunosuppressive regimens and humoral response, except for prednisolone, which was predictive of a reduced response after two (p = 0.001), but not after three doses (p = 0.434). A T-cell response was observed in 50% after two and in 74% after three doses. Despite three vaccine doses, a large proportion of HT recipients exhibits a reduced immune response. Additional strategies are desirable to improve vaccine immunogenicity in this vulnerable group of patients.

Aims Whether sex affects selection for and outcomes after heart transplantation (HTx) remains unclear. We aimed to show sex differences in pre‐transplant characteristics and outcomes after HTx. Methods and results From 1995 to 2019, 49 200 HTx recipients were prospectively enrolled in the Organ Procurement and Transplantation Network. Logistic regression models were used to evaluate clinical characteristics by sex. Multivariable Cox regression models were fitted to assess sex differences in all‐cause mortality, cardiovascular mortality, graft failure, cardiac allograft vasculopathy (CAV), and malignancy. In 49 200 patients (median age 55 years, interquartile range 46–62; 24.6% women), 49 732 events occurred during a median follow‐up of 8.1 years. Men were older than women, had more often ischaemic cardiomyopathy (odds ratio [OR] 3.26, 95% confidence interval [CI] 3.11–3.42; P < 0.001), and a higher burden of cardiovascular risk factors, whereas women had less malignancies (OR 0.47, CI 0.44–0.51; P < 0.001). Men were more often treated in intensive care unit (OR 1.24, CI 1.12–1.37; P < 0.001) with a higher need for ventilatory (OR 1.24, CI 1.17–1.32; P < 0.001) or VAD (OR 1.53, CI 1.45–1.63; P < 0.001) support. After multivariable adjustment, men had a higher risk for CAV (hazard ratio [HR] 1.21, CI 1.13–1.29; P < 0.001) and malignancy (HR 1.80, CI 1.62–2.00; P < 0.001). There were no differences in all‐cause mortality, cardiovascular mortality, and graft failure between sexes. Conclusions In this US transplant registry, men and women differed in pre‐transplant characteristics. Male sex was independently associated with incident CAV and malignancy even after multivariable adjustment. Our results underline the need for better personalized post‐HTx management and care.