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BACKGROUND: Patients with kidney failure on dialysis or after renal transplantation have a high risk for severe COVID-19 infection, and vaccination against SARS-CoV-2 is the only expedient prophylaxis. Generally, immune responses are attenuated in patients with kidney failure, however, systematic analyses of immune responses to SARS-CoV-2 vaccination in patients on dialysis and in kidney transplant recipients (KTRs) are still needed. METHODS: In this prospective, multicentric cohort study, antibody responses to COVID-19 mRNA vaccines (BNT162b2 [BioNTech/Pfizer] or mRNA-1273 [Moderna]) were measured in 32 patients on dialysis and in 28 KTRs. SARS-CoV-2–specific antibodies and neutralization capacity were evaluated and compared with controls (n=78) of a similar age range. RESULTS: After the first vaccination, SARS-CoV-2–specific antibodies were nearly undetectable in patients with kidney failure. After the second vaccination, 93% of the controls and 88% of patients on dialysis but only 37% of KTRs developed SARS-CoV-2–specific IgG above cutoff. Moreover, mean IgG levels were significantly lower in KTRs (54±93 BAU/ml) compared with patients on dialysis (503±481 BAU/ml; P

BackgroundModification of vaccination strategies is needed to improve the immune response to SARS-CoV-2 vaccination in kidney transplant recipients (KTRs).MethodsThis multicenter observational study aimed to determine antibody kinetics among 60 seropositive KTRs and analyzed the effects of the third vaccination against SARS-CoV-2 in 174 previously seronegative KTRs. We investigated whether mycophenolate mofetil (MMF) dose reduction by 25-50% prior the third vaccination influences vaccination success.Results18 of 60 (30%) seropositive KTRs became seronegative in the serological assay within six months. Loss of antibodies was predicted by low initial antibody levels (≤206.8 BAU/ml), older age, and impaired graft function. A third vaccination in previously seronegative KTRs induced seroconversion in 56 of 174 (32.1%) KTRs with median antibody levels 119 (76–353) BAU/ml and median neutralizing capacity titer of 1:10 (0– 1:40). Multivariate logistic regression revealed that initial antibody levels (OR 1.39, 95% CI 1.09–1.76), graft function (OR 0.05, 95% CI 0.01–0.39), time after transplantation (OR 1.04, 95% CI 1.02–1.07) and MMF trough levels (OR 0.43, 95% CI 0.21–0.88) correlated with seroconversion, pConclusionsTemporary reduction in MMF dose might be a promising approach to improve the immune response in KTRs.

Kidney transplant recipients (KTRs) are extremely vulnerable to SARS-CoV-2 infection and show an impaired immune response to SARS-CoV-2 vaccination. We analyzed factors related to vaccination efficiency in KTRs. In a multicenter prospective observational study (NCT04743947), IgG antibodies levels against SARS-CoV-2 spike S1 subunit and their neutralization capacity after SARS-CoV-2 vaccination were analyzed in 225 KTRs and compared to 176 controls. After the vaccination, 56 (24.9%) KTRs became seropositive of whom 68% had neutralizing antibodies. This immune response was significantly lower compared to controls (239 [78-519] BAU/ml versus 1826 [560-3180] BAU/ml for KTRs and controls, p