Impact of ABO compatibility/incompatibility on the perioperative anti-SARS-CoV-2 IgG levels in two preoperatively vaccinated patients undergoing kidney transplantation

Herein, we monitored the perioperative anti-SARS-CoV-2 S IgG titers in patients who were preoperatively vaccinated with two doses of a COVID-19 mRNA vaccine. Additionally, we compared the clinical settings between ABO-incompatible and ABO-compatible pre-emptive kidney transplantation (KTx). Case 1 was of a 45-year-old man who was an ABO-incompatible KTx recipient. Prior to transplantation, his serum antibody titers decreased from 278 U/mL at baseline to 41.9 U/mL after desensitization therapy (84.9% lower) and 54.7 U/mL (80.3% lower) at day 8; it is now maintained at 4.1 U/mL at 6 months post-transplantation (98.5% lower). Case 2 was of a 50-year-old man who was an ABO-compatible KTx recipient. His serum antibody titer level decreased from 786 U/mL at baseline to 386 U/mL on day 8 (50.8% lower) and is now maintained at 156 U/mL at 6 months post-transplantation (80.1% lower). We suggest that anti-SARS-CoV-2 S IgG titers should be monitored during the perioperative period to determine the optimal timing of COVID-19 vaccine booster doses for the maintenance of protective immunity, particularly in ABO-incompatible KTx recipients who require desensitization therapy.