Abstract
BACKGROUND: While anti-SARS-CoV-2 vaccination success in kidney transplant recipients (KTR) after two doses and 1273-mRNA was associated with higher seroconversion rates compared to BNT162b2-mRNA in our "DIA-Vacc Study" (NCT04799808), it remains unclear whether this may also be the case in non-responding KTR after a third vaccination dose. MATERIALS AND METHODS: Non-responding KTR (after two mRNA vaccinations) were investigated 4.5-6 months after study enrollment at first vaccination. One hundred sixty-six of 193 received a third vaccination between 3.5 and 5 months after the initial study enrollment and were always investigated 4 weeks later, exploring humoral immune response (ELISA) and specific cellular responses (interferon-γ release assay). Sixty-seven of 193 measurements in KTR were done immediately before the third vaccination or in KTR without further vaccination at 4.5-6 months. RESULTS: Of 193 KTR with no initial immune response 4 weeks after the second vaccination, 106/87 were immunized twice with 1273-mRNA/BNT162b2-mRNA, respectively. Additional mRNA booster vaccination led to positive seroconversion rates of 30-50%, while 16% of the initial non-responders demonstrated a delayed seroconversion without any booster vaccination. Using logistic regression analysis, a positive IgG response after the third vaccination was 23% more likely if the primary vaccine type was 1273-mRNA compared to BNT162b2-mRNA (OR = 4.420, 95% CI [1.208-16.173], p = 0.025). Primary vaccine type, a weak anti-SpikeS1 IgG response 4 weeks after second vaccination (3.2-35.2 BAU/ml, p < 0.001) and a lack of MMF/MPA as part of the immunosuppressive treatment (trend, p = 0.06) but no other variables studied correlated with seroconversion success. CONCLUSION: This observational study adds important evidence toward using 1273-mRNA as the primary mRNA vaccine type for immunosuppressed KTR.