Humoral Response after SARS-CoV-2 mRNA Vaccination in a Cohort of Hemodialysis Patients and Kidney Transplant Recipients
Authors: Danthu Clément , Hantz Sébastien , Dahlem Arthur , Duval Marion , Ba Bacary , Guibbert Manon , El Ouafi Zhour , Ponsard Séverine , Berrahal Insaf , Achard Jean-Michel , Bocquentin Frédérique , Allot Vincent , Rerolle Jean-Philippe , Alain Sophie , Touré Fatouma 
Published: June 2021

Significance Statement
Data are lacking on the humoral response to COVID-19 vaccination in kidney transplant recipients and patients on hemodialysis. This study of humoral response to an mRNA vaccine in 78 patients undergoing hemodialysis, 74 kidney transplant recipients, and seven healthy controls found that anti–SARS-CoV-2 antibodies peaked at day 36 postvaccination among controls, whereas patients on hemodialysis had lower titers that peaked at day 58, and only three patients who received kidney transplant exhibited detectable antibody levels. Among patients on hemodialysis, age <75 years, serum albumin, and Kt/V were positively correlated with serological response; those who were nonresponders to the HBV vaccine had the lowest anti–SARS-CoV-2 antibody titers. These findings suggest that postvaccination humoral response is strongly inhibited by immunosuppressant therapy in kidney transplant recipients and is reduced by the uremic condition in patients on hemodialysis.

Background
Kidney transplant recipients and patients receiving hemodialysis are immunocompromised populations that are prioritized for COVID-19 vaccination but were excluded from clinical trials of SARS-CoV-2 mRNA vaccines. Antibody titers and rates of seroconversion after vaccination are lower among patients with CKD and those taking immunosuppressants compared with controls. Data are lacking regarding their humoral response to vaccination to prevent COVID-19.

Methods
This investigation of early serological response after COVID-19 vaccination with the Pfizer/BioNTech (BNT162b2) mRNA vaccine included 78 patients undergoing hemodialysis, 74 kidney transplant recipients, and seven healthy controls. We recorded data from the medical file for various clinical parameters, including response to hepatitis B vaccination, and measured antibody titers against SARS-CoV-2 at 0, 14, 28, 36, and 58 days after the first injection.

Results
In controls, we detected antibodies at a positive level (>13 arbitrary units per ml; AU/ml) at day 14 postinjection, which increased progressively to peak at day 36 (1082 AU/ml; interquartile range [IQR], 735.0–1662.0). Patients undergoing hemodialysis had lower titers that peaked at day 58 (276 AU/ml; IQR, 83.4–526.0). We detected a positive antibody level in only three transplant recipients at day 36. In patients on hemodialysis, those aged <75 years had a higher antibody response versus those aged >75 years, and serum albumin and Kt/V were positively correlated with serological response (P<0.04 and P<0.0, respectively); nonresponders to HBV vaccine had the lowest anti–SARS-CoV-2 antibody titers.

Conclusions
Our results suggest that the postvaccination humoral response is strongly inhibited by immunosuppressant therapy in kidney transplant recipients, and is reduced by the uremic condition in patients undergoing hemodialysis.