A Third Dose of SARS-CoV-2 Vaccine Increases Neutralizing Antibodies Against Variants of Concern in Solid Organ Transplant Recipients

A. H. Karaba¹, X. Zhu¹, T. Ling¹, K. H. Wang¹, A. G. Rittenhouse¹, O. Akinde¹, Y. Eby¹, J. E. Ruff¹, J. N. Blankson¹, A. T. Abedon¹, J. L. Alejo¹, A. L. Cox¹, J. R. Bailey¹, E. A. Thompson¹, S. L. Klein¹, D. S. Warren¹, J. M. Garonzik-Wang², B. J. Boyarsky¹, I. Sitaras¹, A. Pekosz¹, D. L. Segev¹, A. A. Tobian¹, W. A. Werbel¹

¹Johns Hopkins University, Baltimore, MD, ²University of Wisconsin School of Medicine and Health, Madison, WI

Meeting: 2022 American Transplant Congress

Abstract number: 688

Keywords: Antibodies, COVID-19, Vaccination

Topic: Clinical Science » Infection Disease » 24 - All Infections (Excluding Kidney & Viral Hepatitis)

Session Information

Session Name: All Infections (Excluding Kidney & Viral Hepatitis) I

Session Type: Poster Abstract

Date: Saturday, June 4, 2022

Session Time: 5:30pm-7:00pm

Presentation Time: 5:30pm-7:00pm

Location: Hynes Halls C & D

*Purpose: Vaccine-induced SARS-CoV-2 antibody responses are attenuated in solid organ transplant recipients (SOTRs) and breakthrough infections are more common. Additional SARS-CoV-2 vaccine doses increase anti-spike IgG in some SOTRs, but it is uncertain whether neutralization of variants of concern (VOCs) is enhanced, and whether anti-spike IgG correlates with neutralization of these VOCs. The purpose of this study was to determine how a third dose of SARS-CoV-2 vaccine augments the antibody response to VOCs and compare this response to that of healthy controls.

*Methods: Antibody responses in 47 SOTRs were assessed using clinical (Euroimmun) and research (Meso Scale Diagnostics, MSD) anti-spike IgG, pseudoneutralization (ACE2 blocking), and live-virus neutralization (nAb) against VOCs before and after a third SARS-CoV-2 vaccine dose (70% mRNA, 30% Ad26.COV2.S) with comparison to 15 healthy controls after two mRNA vaccine doses. We used correlation analysis to compare anti-spike IgG assays and focused on thresholds associated with neutralizing activity.

*Results: Overall, a third SARS-CoV-2 vaccine dose increased median anti-spike (1.6-fold) and receptor-binding domain (1.5-fold) IgG in SOTRs, as well as pseudoneutralization against VOCs (2.5-fold versus Delta). However, IgG and neutralizing activity were significantly lower than in healthy controls (p<0.001), with 32% of SOTRs having zero detectable nAb against Delta even after third vaccination. Linear correlation with of anti-spike IgG with nAb emerged at IgG >4 Arbitrary Units (AU) on the clinical assay and >10^4 AU on the research assay (Figure).

*Conclusions: These findings highlight (1) benefits of a third vaccine dose for some SOTRs, (2) strong correlation between neutralization and surrogate assays above specific thresholds, and (3) the need for alternative strategies to improve protection in a significant subset of this population who remain at high risk for COVID-19.

To cite this abstract in AMA style:

Karaba AH, Zhu X, Ling T, Wang KH, Rittenhouse AG, Akinde O, Eby Y, Ruff JE, Blankson JN, Abedon AT, Alejo JL, Cox AL, Bailey JR, Thompson EA, Klein SL, Warren DS, Garonzik-Wang JM, Boyarsky BJ, Sitaras I, Pekosz A, Segev DL, Tobian AA, Werbel WA. A Third Dose of SARS-CoV-2 Vaccine Increases Neutralizing Antibodies Against Variants of Concern in Solid Organ Transplant Recipients [abstract]. Am J Transplant. 2022; 22 (suppl 3). https://atcmeetingabstracts.com/abstract/a-third-dose-of-sars-cov-2-vaccine-increases-neutralizing-antibodies-against-variants-of-concern-in-solid-organ-transplant-recipients/. Accessed May 18, 2025.

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