Rapid Decline in Vaccine-induced Anti-SARS-CoV-2 Antibody Titers 3 Months After Kidney Transplantation: A Case Series From Belgium

We and others previously reported persistent immunogenicity of anti-severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccines in the first month after kidney transplantation (KT) with, nevertheless, a significant drop in antibody (Ab) titer.^1-3 However, the mid-term impact of starting immunosuppression for KT on Ab titers has not been described yet.

We report the evolution of anti-SARS-CoV-2 Ab titer 100 d after KT in 14 KT recipients (KTRs) transplanted between January 2021 and June 2021 who received at least 1 vaccine dose before KT.

We assessed the antireceptor-binding domain Ab titers (Elecsys anti-SARS-CoV-2, Roche Diagnostics GmbH, Mannheim, Germany; positive threshold ≥0.8 U/mL) on the day of transplantation (day 0), 28 d after transplantation (day 28), and 100 d after transplantation (day 100). This work received institutional review board approval.

Ten patients had received their second dose of either the mRNA BNT162b2 (Pfizer-BioNTech, n = 8) or ChAdOx1 nCoV-19 vaccine (AstraZeneca, n = 2) at a mean time of 57 (range, 25–78) d before KT.¹ Four patients had received a single dose of vaccine (Pfizer-BioNTech n = 2, AstraZeneca n = 2) at a mean time of 29 (range, 13–50) d before KT, of which 2 patients received a second dose of the same vaccine 2 mo after KT. The mean age was 58 (range, 32–77) y; 57% were male. Twelve patients were on dialysis before transplantation (mean duration, 54 [range, 20–122] mo). One patient had prior history of coronavirus disease 2019 (COVID-19).

Sensitized patients (n = 3) and KTRs who received a graft from a living donor (n = 2) were inducted with thymoglobulin and basiliximab, respectively. All patients received an association of tacrolimus, mycophenolate, and steroids. None developed COVID-19 infection to date.

Anti-SARS-CoV-2–receptor-binding domain (RBD) Ab levels significantly decreased from day 0 to 100, with mean (±SEM) titers at 1124 ± 441, 514 ± 205, and 146 ± 39 U/mL at day 0, 28, and 100, respectively (Figure 1). Compared with day 0, it represents a 54% (P = 0.0034) and 87% (P = 0.0015) drop in Ab titers at day 28 and 100, respectively. The patient with a history of COVID-19 before KT showed a similar decline (54% and 85% drop at day 28 and 100, respectively). Of the 4 patients who had received a single dose of vaccine, 2 had no detectable Ab on day 100 (despite one of them receiving a second dose in the meantime) and 2 had very low Ab titers (<1.5 U/mL). Similar to our previous report,¹ the Ab titer drop was not significantly different in patients inducted with thymoglobulin (n = 3) or basiliximab (n = 2) compared with the others (90% and 82% drop, respectively, versus 86% at day 100).

FIGURE 1.: Evolution of anti-RBD antibody titer. Mean (±SEM) antibody titer on d 0, 28, and 100: 1124 (±441), 514 (±205), and 146 (±39) U/mL (P = 0.003, 0.002; Wilcoxon test). RBD, receptor-binding domain; SEM, standard error of the mean.

Our results contrast with the long-term persistent humoral response in immunocompetent hosts.⁴ Doria-Rose et al showed that anti-SARS-CoV-2-RBD Ab activity remained high 6 mo after the second dose of mRNA-1273 vaccine. This suggests that immunosuppressive therapy hinders the immunization rate in KTRs⁵ and reduces the mid-term immunogenicity of mRNA vaccines administered before KT, which highlights the clinical relevance of a booster dose of vaccine early after KT. The optimal timing to administrate this additional dose needs further investigation.