To the editor:

Anti–severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccination is recommended in patients who underwent a transplant because of an increased risk of developing severe coronavirus disease 2019 (COVID-19), and mortality.¹ Because of a weak immunogenicity of mRNA 2-dose vaccines in transplant patients, the French Health Authority recommended to offer a third dose to immunosuppressed patients to boost the immune response.^{2 , 3} However, no biological monitoring before and after vaccination is recommended. We report on the case of a 23-year-old non–human leukocyte antigen–sensitized patients who underwent a kidney transplant who presented an acute rejection after the second dose of the BNT162b2 mRNA COVID-19 Vaccine (Pfizer-BioNTech). She had undergone a deceased donor kidney transplantation for nephronophthisis 18 months earlier. The post-transplant period was uneventful. Her maintenance therapy was based on tacrolimus (target trough level, 5 ng/ml and 7 ng/ml), mycophenolic acid, and low-dose steroid. Fifteen days before the first dose, her serum creatinine level was at 80 μmol/L and anti–SARS-CoV-2 serology was negative. Eight days after the second dose, systematic blood tests revealed impaired kidney function at 130 μmol/L, which then raised to 360 μmol/L (Figure 1 ). A kidney biopsy revealed a cellular acute rejection. Donor-specific anti–human leukocyte antigen antibodies became detectable with a weak intensity, targeting donor human leukocyte antigen class II antigens. Anti–SARS-CoV-2 spike protein antibodies became positive. Tacrolimus trough level was unchanged at 5 ng/ml. At 10 days, after steroid pulses (500 mg/d for 3 days), the patient’s serum creatinine level had decreased to 230 μmol/L. Another kidney biopsy is planned to discuss the use of polyclonal antibodies. Hence, this report suggests that kidney function should be carefully monitored in kidney transplantation undergoing anti–SARS-CoV-2 vaccination, especially if a third boost dose is performed.

Figure 1

(a) Outcome of kidney function before and after transplantation and (b,c) kidney pathology. Trichrome Masson staining exhibited inflammatory infiltration, tubulitis, edema, and peritubular capillaritis (original magnification ×20 [b] and ×40 [c]). Kidney biopsy was scored as follows, according to the Banff 2019 classification⁴: i2, t2, v0, g0, ptc1, ti1, i-IFTA0, C4d0, cg0, mm0, ah1, cv0, ci0, ct0. To optimize viewing of this image, please see the online version of this article at www.kidney-international.org.