COVID-19 Vaccine Seroresponse Based on The Timing of The Primary Series; Pre- versus Post-Renal Transplantation.

Background: Coronavirus disease 2019 (COVID-19) poses a serious risk to patients with chronic kidney disease (CKD) and renal transplant. While COVID-19 vaccination is recommended before transplant, there are limited data comparing vaccine timing. Our aim is to evaluate serological responses to COVID-19 vaccines pre- and post-renal transplant and the durability of antibody levels.

Methods: We retrospectively evaluated the antibody response of adult renal transplant recipients who had received at least a primary series of the COVID-19 vaccine. The patients were divided into two groups based on the timing; pre- or post-transplant. Antibody titer levels were evaluated at least 4 weeks after vaccination for each group. Titer durability was assessed by calculating the median titer level of individuals.

Results: A total of 139 patients were identified between January 2019 and April 2022. Twenty-nine patients were excluded because of previous COVID-19 infection, and 15 patients were excluded each for insufficient vaccine doses and lack of titer data. Forty patients were included for the pre-transplant group and 40 for post-transplant. The number of pre-transplant patients who developed antibodies (39 patients, 97.5%) was significantly greater than the number of post-transplant patients (21 patients, 52.5%) with p < .01. The median post-vaccination titer levels were significantly greater in the pre-transplant group up to 5 months after vaccination (p < .05). The pre-transplant group's titers seemed sustained even after renal transplantation.

Conclusion: Vaccinating renal transplant patients before transplant results in increased achievement of seroresponse, higher levels of antibody titers, and sustained titers following transplant. Larger and prospective studies are warranted to confirm the findings.