Immunogenicity of the BNT162b2 mRNA Vaccine in Heart Transplanted Patients-A Prospective Cohort Study.

Itzhaki Ben Zadok, Osnat; Shaul, Aviv A; Ben-Avraham, Binyamin; Yaari, Vicky; Ben Zvi, Haim; Shostak, Yael; Pertzov, Barak; Eliakim-Raz, Noa; Abed, Galia; Abuhazira, Miriam; Barac, Yaron D; Mats, Israel; Kramer, Mordehay; Aravot, Dan; Kornowski, Ran; Ben-Gal, Tuvia

AIMS To assess the short-term immunogenicity to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) mRNA vaccine in a population of heart transplanted (HTx) recipients. METHODS A prospective single-center cohort study of HTx recipients who received a 2-dose SARSCoV-2 mRNA vaccine (BNT162b2, Pfizer-BioNTech). Whole blood for anti-spike IgG (S-IgG) antibodies were drawn at days 21-26 and at days 35-40 after the first vaccine dose. Geometric mean titers (GMT) ≥50 AU/mL were interpreted positive. RESULTS Included were 42 HTx recipients at a median age of 61 (IQR 44, 69) years. Median time from HTx to the 1st vaccine dose was 9.1 (IQR 2.6, 14) years. Only 15% of HTx recipients demonstrated the presence of positive S-IgG antibody titers in response to the 1st vaccine dose (GMT 90 (IQR 54, 229) AU/mL). Forty-nine percent of HTx recipients induced S-IgG antibodies in response to either the 1st or the full 2-dose vaccine schedule (GMT 426 (IQR 106, 884) AU/mL). Older age (68 (IQR 59, 70) years vs. 46 (IQR 34, 63) years, p=0.034) and anti-metabolites-based immunosuppression protocols (89% vs. 44%, p=0.011) were associated with low immunogenicity. Importantly, 36% of HTx recipients who were non-responders to 1st vaccine dose became S-IgG seropositive in response to the 2nd vaccine dose. DISCUSSION Approximately a half of HTx recipients did not generate S-IgG antibodies following SARSCoV-2 2-dose vaccine. The generally achieved protection from SARSCoV-2 mRNA vaccination should be regarded with caution in the population of HTx recipients. The possible benefit of additive vaccine doses should be further studied.