Humoral Response of Renal Transplant Recipients to the BNT162b2 SARS-CoV-2 mRNA Vaccine Using Both RBD IgG and Neutralizing Antibodies

Hod, Tammy; Ben-David, Aharon; Olmer, Liraz; Levy, Itzchak; Ghinea, Ronen; Mor, Eytan; Lustig, Yaniv; Rahav, Galia

Background: Data about SARS-CoV-2 vaccines efficacy in renal transplant recipients (RTR) is lacking. Methods: To reveal predictors for humoral response to BNT162b2 vaccine among RTR, patients were divided to positive (N=42) and negative (N=78) response groups based on receptor-binding domain (RBD) IgG >= 1.1 and neutralizing antibodies (NA) >= 16 dilution versus RBD IgG < 1.1 or NA < 16 respectively. NA were detected using a SARS-CoV-2 pseudo-virus. Results: NA were detected in only 42/120 (35%) of RTR vs. 197/202 (97.5%) immunocompetent controls (p < 0.001). NA geometric mean titers (GMTs) in RTR were significantly lower vs. the control group [83.7 (95% CI 50.5-138.8) vs. 482 (95% CI 411-566), p < 0.001]. In a multivariable analysis, mycophenolic acid (MPA) dose and hemoglobin (Hb) level were found to be independent predictors for antibody response in RTR. A positive response rate of 27% vs. 63% was observed in patients on and off MPA, respectively. An increase in MPA dose by 1 mg/kg weight reduced the odds for a positive response by 17% (OR 0.83, 95% CI 0.75-0.92, p<0.001). GMTs for RBD IgG were significantly reduced as MPA daily dose increased. Hb blood level < 13 g/dL reduced the antibody response by 63% (p=0.04). Pain at the injection site after the second vaccine dose was significantly higher in the responders vs. nonresponders (20.5% vs. 5.5%, p=0.01). Conclusions: Only 35% of RTR develop NA to the BNT162b2 mRNA vaccine. MPA is a major suppressor of antibody response in RTR.