Immunogenicity of the BNT162b2 mRNA Vaccine in heart transplanted Patients- a prospective cohort study

Osnat Itzhaki Ben Zadok ^1,2 Aviv Shaul ^1,2 Binyamin Ben-Avraham ^1,2 Vicky Yaari ^1,2 Haim Ben Zvi ^2,3 Yael Shostak ^2,4 Barak Pertzov ^2,4 Noa Eliakim-Raz ^2,5 Galia Abed ^1,2 Miriam Abuhazira ^2,6 Yaron Barac ^2,6 Israel Mats ^1,2 Mordehay Kramer ^2,4 Dan Aravot ^2,6 Ran Kornowski ^1,2 Tuvia Ben-Gal ^1,2

¹Department of Cardiology, Rabin Medical Center, Israel
²Sackler School of Medicine, Tel-Aviv University, Israel
³Department of Microbiology, Rabin Medical Center, Israel
⁴Department of Pulmonology, Rabin Medical Center, Israel
⁵Department of Infectious Diseases, Rabin Medical Center, Israel
⁶Department of Cardio-Thoracic Surgery, Rabin Medical Center, Israel

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) patients.

Methods: A prospective single-center cohort study of HTx patients 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 considered positive.

Results: Included were 42 HTx patients 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 patients 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 patients induced SARSCoV-2 neutralizing antibodies in response to either the 1st or 2nd vaccine doses (GMT 426 (IQR 106, 884) AU/mL). Importantly, 36% of patients became S-IgG seropositive in response to the 2nd, but not the first, vaccine dose.

Discussion: Approximately a half of HTx patients did not generate neutralizing antibodies following SARSCoV-2 2-dose vaccine. The generally achieved protection from SARS-CoV-2 attributed to the SARSCoV-2 mRNA vaccination should be regarded with caution in the population of HTx patients. The possible benefit of future booster vaccine doses based on GMT levels should be further studied.