5687 SARS-COV-2 PREEXPOSURE PROTECTS FROM IMMUNITY-FADING AFTER MRNA VACCINATION IN KIDNEY TRANSPLANT RECIPIENTS, DIALYSIS PATIENTS, AND MEDICAL PERSONNEL

Abstract Background and Aims Immunity development and fading after SARS-CoV-2mRNA vaccination differently affects high risk populations such as dialysis or renal transplant patients compared to general population. We hypothesized that COVID-19 preexposure influences not only vaccination dependent development of immunity but also protects from immunity fading depending on vaccine type and patient group. Method We evaluated two and nine months follow up data in our observational DIA-Vacc study exploring specific cellular (interferon-γ release assay = IGRA) or/and humoral immune responses after 2x SARS-CoV-2mRNA vaccination in 2615 participants including medical personnel (300 MP), dialysis patients (1831 DP), kidney transplant recipients (484 KTR). Study participants were separated into COVID-19 preexposure positive (n = 405) versus negative (n = 2210) groups, where symptomatic or asymptomatic COVID-19 disease before start of vaccination was confirmed by clinical symptoms, PCR positivity and/or Spike S1/core antiSARS-CoV-2 antibodies. Results Two months (T2) after first vaccination, seroconversion and T-cell immunity success rates for MP and DP were excellent (86-100%) and independent on COVID-preexposure. In KTR, vaccination-related seroconversion rate on T2 almost doubled with COVID-preexposure (84% versus 45% without), a result consistent with all different antibody measurements (IgA, IgG, or receptor binding domain-RBD). Nine months after first vaccination in COVID-19 negative study patients, the percentage of patients with RBD-antibody fading results >50% remained low in MP (18%), high in DP (53%) and intermediate in KTR (39%). In contrast, in all patient groups with COVID-19 preexposure RBD-antibody fading reactions >50% within nine months after vaccination were almost vanished (4% in MP, 8% in DP and 0% in KTR). COVID-19 preexposure in DP also reduced T-cell immunity fading as measured by IGRA, where only 9% of patients showed a >50% titer decrease compared to 34% of DP without any COVID-19 preexposure. Similar results were also seen regarding vaccination dependent regulation of antiSARS-Cov-2 IgG antibodies dependent on COVID-19 preexposure. These results are also reflected by increased mean antibody titers for IgG- and RBD-antibodies nine months after vaccination in all COVID-19 preexposed compared to non-exposed groups. In addition, the degree of antibody fading after vaccination was not just dependent on COVID-19 preexposure status but also on mRN