Annual immunisation against COVID-19 and seasonal influenza before the winter waves is increasingly recommended in routine practice. These vaccines may be administered on the same day or sequentially, yet data on the immunogenicity of consecutive vaccinations in patients on dialysis remain limited. In this real-world observational study, we assessed SARS-CoV-2-specific immune responses in dialysis patients receiving the monovalent XBB.1.5-vaccine followed by a quadrivalent influenza vaccine 14 days later, or either vaccine alone. Antigen-specific antibodies and T cells were quantified using enzyme-linked immunosorbent assays and flow cytometry. Baseline analyses showed that most patients had detectable SARS-CoV-2- and influenza-specific immunity prior to the vaccination season. Both vaccines substantially boosted pre-existing humoral and cellular responses. Among XBB.1.5-vaccinated patients, subsequent influenza vaccination did not alter the magnitude of spike-specific antibody or T-cell responses. Likewise, influenza vaccination had no non-specific effect on SARS-CoV-2-specific immunity. Spike-specific responses remained stable for six months and persisted at levels exceeding those of unvaccinated patients assessed during the same period. Sequential administration of COVID-19 and influenza vaccines in patients on dialysis is feasible and was not associated with compromised immunogenicity of either vaccine. These findings support the use of booster vaccination in these patients and inform future deployment of additional mRNA-based vaccines.

The continuous evolution of SARS-CoV-2 raises concerns about immune escape from preexisting immunity. The monovalent JN.1adapted mRNA vaccine was developed to better match circulating variants, yet data on its ability to induce and broaden humoral and cellular immunity in individuals with or without prior infection remain limited. We recruited 37 immunocompetent adults before and two weeks after JN.1 vaccination to assess vaccine-induced immunity. Spike-specific CD4 and CD8 T cells were quantified following stimulation with spike-derived peptides from the parental strain, XBB.1.5, and JN.1, and their CTLA-4 expression and cytokine profiles were analyzed by flow cytometry. Spike-specific IgG and neutralizing activity against authentic parental, XBB.1.5, JN.1, and KP.3.1.1 isolates were also measured. JN.1 vaccination significantly increased spike-specific CD4+ and CD8+ T-cell frequencies with comparable cytokine profiles across variants and enhanced CTLA-4 expression. IgG levels and neutralizing titers rose markedly, with the strongest relative increases against Omicron lineage variants. Prior infection was associated with higher neutralizing titers but did not influence T-cell responses. Influenza vaccine co-administration had no adverse effect on JN.1 immunogenicity. These findings indicate that hybrid immunity enhances antibody-mediated protection, while robust, cross-reactive T-cell responses may contribute to sustained protection against severe disease irrespective of infection history.

This prospective study investigated whole blood-based immune cell biomarkers for pulmonary tuberculosis (TB) immunoprofiling. Blood samples from 34 healthy controls and 51 tuberculosis patients were analyzed at three timepoints: Prior to therapy (T0), after 14 days of therapy (T1), and at the end of treatment (Te). Using multiparameter flow cytometry, 386 immune cell populations were analyzed. Predictive models were developed using two machine learning algorithms. A TB5LF change score, which was based on five cell populations, effectively distinguished tuberculosis patients from controls (AUC = 0.89) and tuberculosis patients before and at the end of treatment (AUC = 0.92). Similarly, the TB5Lasso score distinguished tuberculosis patients from controls (AUC = 0.91) and tuberculosis patients before and at the end of treatment (AUC = 0.93) but was inversely correlated with disease severity (r=–0.43). Both scores included PD-L1+CD80- neutrophils and PD-L1+HLA-DR+ CD4+ lymphocytes, highlighting PD-L1-associated and Th1-related immune signatures as candidate biomarkers for TB immunoprofiling. These findings are exploratory and hypothesis-generating, providing a basis for future studies evaluating their potential utility in diagnostic and therapy-monitoring contexts.

PURPOSE:High-performance sports training has been associated with immunomodulatory activity on vaccine-induced immunity in athletes. To date, it is unknown whether training in athletes may affect immunogenicity of mRNA-based vaccines, as the vaccine antigen is produced in the muscle. METHODS:In an observational study, 57 athletes and 57 controls were recruited before and 2 weeks after the second vaccination with a COVID-19 mRNA vaccine. Spike-specific IgG antibodies were quantified using enzyme-linked immunosorbant assay. Quantitative and functional characterization of SARS-CoV-2-specific T cells was carried out from whole blood using flow cytometry. Adverse events within the first 7 days after the first and the second vaccination were self-reported using a diary. RESULTS:Levels of anti-spike IgG antibodies were similar in athletes (5766 (interquartile range, 4923) BAU·mL -1 ) and controls (6677 (interquartile range, 6741) BAU·mL -1 , P = 0.317), which also held true for neutralizing activity ( P = 0.185). In contrast, athletes reached significantly lower levels of spike-specific CD4 ( P = 0.0001) and CD8 T cells ( P = 0.025). Although most individuals from both groups had spike-specific CD4 T-cell levels above detection limit, the percentage of individuals with detectable CD8 T cells was significantly lower among athletes (23/57 (40.4%)) compared with controls (35/57 (61.4%), P = 0.039). Cytokine expression profiling showed no major differences between the groups, whereas the expression of CTLA-4 was significantly lower in spike-specific CD4 T cells of athletes. Overall, adverse events were similar among the groups except for more athletes reporting swelling at the injection site and headache. CONCLUSIONS:COVID-19 mRNA vaccination was well tolerated and induced a strong humoral and cellular immune response in both athletes and controls. The significantly lower levels of vaccine-specific T cells with less CD8 T-cell responders among athletes may indicate mRNA vaccine-specific alterations in immune responses related to high-performance sports training.

Background. Cytomegalovirus-specific immunoglobulins (CMV-IVIg) can contribute to viral control after transplantation. Apart from neutralizing antiviral activity, knowledge on their potential indirect effects on the restoration of virus-specific T-cell immunity is limited. Therefore, we tested whether CMV-IVIg may affect cytokine induction and proliferation of CMV-specific T cells in vitro. Methods. Blood samples of 38 individuals (23 kidney transplant recipients and 15 immunocompetent controls) were stimulated using CMV antigens in saturating and low antigen concentration, or with the polyclonal stimulus Staphylococcus aureus enterotoxin B in the presence or absence of CMV-IVIg. CD4 and CD8 T-cell effector function, including the induction of cytokines interferon-gamma, tumor necrosis factor, and interleukin-2, was characterized after 6 h, and specific proliferation was quantified after 5 d using flow cytometry. Results. Irrespective of antigen concentration, the presence or absence of CMV-IVIg had no effect on the percentage of CMV-specific CD4 and CD8 T cells producing interferon-gamma, tumor necrosis factor, or interleukin-2. However, proliferation of CMV-specific CD3 T cells, including CD4 and CD8 T-cell subpopulations, was significantly higher in the presence of CMV-IVIg at both saturating (P = 0.007) and low antigen concentrations (P = 0.022). In contrast, a lower percentage of both cytokine-producing T cells (P < 0.0001) and proliferating T cells (P < 0.0001) was observed in the presence of CMV-IVIg after polyclonal stimulation. Conclusions. CMV-IVIg did not have any effect on immediate T-cell effector function. However, the marked effect of CMV-IVIg on increasing the proliferation of CMV-specific T cells while concomitantly reducing polyclonal T-cell function may have implications for the therapeutic use of immunoglobulins to restore CMV-specific T cells in patients with active CMV infection without increasing the alloreactive burden.

Annual immunisation against both COVID-19 and seasonal influenza is now becoming standard of care, particularly ahead of anticipated winter waves. These vaccines may be co-administered on the same day or sequentially on separate days. Data on immunogenicity and the impact of consecutive vaccinations on spike-specific humoral and cellular immunity in dialysis patients remain limited. In this real-world observational study, SARS-CoV-2-specific immune responses were evaluated in dialysis patients receiving the monovalent XBB.1.5 vaccine followed by a quadrivalent influenza vaccine 14 days later, or either vaccine alone. Specific antibodies and T-cells were quantified and characterized using enzyme-linked immunosorbent assay and flow-cytometry. Baseline analyses from a reference-group prior to the vaccination season showed that most patients had detectable SARS-CoV-2- and influenza-specific immunity. Both the XBB.1.5 and the influenza vaccine substantially enhanced pre-existing antigen-specific humoral and cellular responses. When comparing XBB.1.5-vaccinated patients with and without subsequent influenza-vaccination, the magnitude of XBB.1.5-induced antibody or T-cell responses did not differ. Likewise, the influenza-vaccine had no non-specific effect on SARS-CoV-2-specific immune responses. Finally, spike-specific immunity remained stable over a six-month period and persisted at levels exceeding those of unvaccinated patients assessed during the same period. In conclusion, sequential administration of COVID-19 and influenza vaccines in dialysis patients is feasible and does not compromise the immunogenicity of either vaccine. Our data are encouraging in the context of ongoing development of additional mRNA-based vaccines that may require administration in close temporal proximity to seasonal influenza immunisation, and underscore the benefit of booster vaccination in individuals with impaired immune function. ### Competing Interest Statement M.S. has received grant support from Astellas and Biotest to the organization Saarland University outside the submitted work, and honoraria for lectures from Biotest, Takeda, Qiagen, MSD, and served in advisory boards for Moderna, Biotest, MSD and Takeda. T.S. has received travel support from Biotest. All other authors of this manuscript have no conflicts of interest to disclose. ### Funding Statement Financial support was provided in part by the State chancellery of the Saarland to M.S., by the German Federal Ministry of Education and Research (COVIM 2.0, FKZ 01KX2121) to M.S., and by the Dr. Rolf M. Schwiete Stiftung (Project #2023-047) to T.S. ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: The study was performed in adherence to the declaration of Helsinki and approved by the ethics committee of the Aerztekammer des Saarlandes (reference 76/20 including amendments). I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes All data produced in the present study are available upon reasonable request to the authors.

Persistent symptoms following SARS-CoV-2 infection, known as post-COVID syndrome (PCS), severely affect patients’ quality of life. Despite its prevalence, the underlying mechanisms and reliable biomarkers remain elusive. We investigated the antibody response and epitope recognition patterns in PCS to uncover potential biomarkers and pathophysiological links to immune dysregulation. Humoral immune responses were analyzed in PCS patients (n = 64) and convalescent controls (n = 64), matched for sex, age, and time since acute infection, further corroborated in three independent PCS validation cohorts (n = 420). PCS was associated with significantly elevated levels of neutralizing IgG, IgA and IgM antibodies targeting the SARS-CoV-2 receptor-binding domain and spike subdomains, but not against nucleocapsid or seasonal coronaviruses. Next, we identified three discriminatory PCS-specific spike epitopes, primarily located in the membrane-proximal region, as demonstrated by customized peptide microarray, ELISA and luminex methods. Binary logistic regression analysis revealed 82.8% specificity and 60.0% sensitivity for PCS diagnosis in seropositive patients. PCS-specific antibody levels correlated directly (D-Dimers) or inversely (6 min-walk distance, diffusion capacity) with clinical markers. These findings highlight enhanced spike-specific humoral responses in PCS and propose novel epitope-based biomarkers for PCS diagnosis and mechanistic insights. This project was supported by the German Ministry of Education and Research (BMBF; grant no. 01EP2105A). Viral Immunology (VIR)

BACKGROUND:For CMV high-risk constellations, guidelines recommend 3-6 months of prophylaxis with valganciclovir (VGCV). Management in preventing CMV primary infection in patients developing VGCV-associated leukopenia remains challenging. METHODS:We retrospectively analyzed the development of leukopenia during VGCV prophylaxis in 57 seronegative kidney recipients of a CMV-seropositive donor between 2008 and 2021. We analyzed CMV risk and development of CMV-specific T cells in the first post-transplant year depending on leukopenia during VGCV prophylaxis and management with CMV-IVIg. RESULTS:Leukopenia developed in 19/57 patients, with a significant difference in leukocyte counts occurring after 10 weeks of VGCV prophylaxis compared to patients without leukopenia (p = 0.0003). VGCV discontinuation led to leukocyte reconstitution, which tended to be faster in patients receiving additional prophylaxis with CMV-IVIg after VGCV discontinuation (n = 11, p = 0.083). In the first post-transplant year, patients with leukopenia had no higher risk for severe CMV events. Interestingly, patients receiving CMV-IVIg prophylaxis showed a significantly lower peak CMV-load during primary infection (p = 0.040), with no difference in CMV-specific T-cell levels compared to patients without leukopenia or patients with additional CMV-IVIg prophylaxis (p = 0.972). Patients developing adequate CMV-specific T-cell responses less frequently underwent CMV reactivation 50 days following primary infection. CONCLUSION:Leukopenia developed late during VGCV prophylaxis and did not result in an increased risk for CMV primary infections or severe disease. Leukopenic patients receiving CMV-IVIg tended to have a faster leukocyte reconstitution and had lower peak DNAemia, which did not adversely affect CMV-specific T-cell induction. CMV-IVIg may therefore be considered as an alternative prophylactic strategy in patients with VGCV-associated leukopenia.

BACKGROUND:Immune induction under B-cell depletion is complex and far from being fully understood. METHODS:We investigated clinical and immunological responses after dual homologous mRNA vaccination with BNT162b2 and after booster vaccination or infection in 14 B-cell depleted patients with inflammatory central nervous system disease in comparison to 28 healthy controls. Spike-specific IgG were determined using ELISA and neutralizing activity by surrogate assay. Reactive T cells were flow-cytometrically analyzed after spike-specific and polyclonal stimulation. Reactogenicity was self-reported using a questionnaire. RESULTS:Vaccination was well tolerated, with slightly more systemic events reported by patients. Spike-specific antibodies were induced in all controls, but only 43% of patients with significantly lower IgG levels and reduced neutralizing capacity (p < 0.0001). In contrast, spike-reactive T cells were induced in both groups with similar CD4 and higher CD8 T-cell levels in patients. Functional characterization of spike-reactive T cells revealed equally high CTLA-4 expression in both groups, but higher proportions of polyfunctional, triple-cytokine expressing CD4 and CD8 T cells in patients especially after the third immunization. Three patients experienced mild breakthrough infections after second vaccination. CONCLUSIONS:Despite limited ability of B-cell depleted patients to mount a humoral immune response after multiple doses of SARS-CoV-2 mRNA vaccination, the vaccine-induced T-cell response is robust, which may have implications for protection against severe disease.

Respiratory syncytial virus (RSV) prefusion F-based vaccines have recently been approved for immunosuppressed individuals, but data in solid organ transplant (SOT) recipients remain limited. This observational study assessed natural RSV immunity among 52 controls and 197 patients with immunodeficiencies, of which 46 kidney transplant recipients, 30 lung transplant (LuTx) recipients, and 19 patients with chronic kidney disease subsequently received a single dose of a protein-based RSV vaccine to quantify and characterize RSV-specific antibodies and T cells pre- and postvaccination using enzyme-linked immunosorbent assay and flow cytometry. Reactogenicity was self-reported. Over 90% had natural pan-RSV-specific immunoglobulin G, and 30% to 58% had RSV-specific CD4 T cells. Vaccination was well tolerated and led to a significant increase in antibodies and polyfunctional CD4 T cells (P < .0001), with similar T cell levels to both RSV-subtypes A and B. CD4 T cell responses were comparable between kidney transplant and patients with chronic kidney disease, but significantly lower in LuTx recipients (P = .023) and in SOT recipients within the first year posttransplant (P = .005). The vaccine did not induce any CD8 T cells. In conclusion, a single RSV vaccine dose induced strong immunoglobulin G and CD4 T cell responses with RSV-A/B cross-reactivity. However, LuTx and early posttransplant SOT recipients showed reduced T cell responses. Alternative strategies may be required to improve immunogenicity in heavily immunosuppressed SOT recipients.

Primary cholesteatoma is a rare pathology of the ear in childhood, which is characterized by a high recurrence rate. The spread of keratinizing squamous epithelium in the middle ear space with subsequent bone destruction occurs in these cases, in contrast to acquired cholesteatoma, without a retraction pocket as a prerequisite of the disease. In order to better understand the pathogenesis and thus have the chance to develop better therapy concepts, we analyzed our patient population. In the past 10 years, 5 children with primary cholesteatoma have been treated in our clinic. All children were males (ages 3-8 years). 2 of 5 had bilateral cholesteatomas. An asymptomatic coagulation factor deficiency was also diagnosed in 3 of 5 patients (2 children with a disorder in the exogenous system and one with a disorder in the exogenous and endogenous systems). All children received interdisciplinary care. Based on our patient group, the increased risk of male patients developing this pathology can be confirmed. The association between ear pathology and coagulation factor deficiency is an indication that special attention should be paid to impaired hemostaseology in the affected children. Further work is necessary in the areas of therapy as well as the preventive measures for this pathology, in order to further optimize the treatment of these children.

Das primäre Cholesteatom ist eine seltene Pathologie des Ohres im Kindesalter, die von einer großen Rezidivrate gekennzeichnet ist. Die Ausbreitung von verhornendem Plattenepithel in den Mittelohrräumen mit konsekutiven Knochendestruktionen tritt, im Gegensatz zum erworbenem Cholesteatom, in diesen Fällen ohne Retraktionstasche als Vorbote der Erkrankung auf. Um die Pathogenese besser zu verstehen und somit die Chance zu haben bessere Therapiekonzepte zu entwickeln, analysierten wir unser Patientenkollektiv. In den vergangenen 10 Jahren wurden in unserer Klinik 5 Kinder mit einem primären Cholesteatom operativ behandelt. Alle Kinder waren männlich (Alter 3-8 Jahre). 2 von 5 wiesen bilateral Cholesteatome auf. Bei 3 von 5 Patienten konnte zusätzlich ein asymptomatischer Gerinnungsfaktorenmangel (2 Kinder mit Störung im exogenen System und eins mit Störung im exogenen und endogenen System) diagnostiziert werden. Eine interdisziplinäre Betreuung erfolgte bei allen Kindern. Anhand unserer Patientengruppe kann das erhöhte Risiko für männliche Patienten, an der Pathologie zu erkranken, bestätigt werden. Die Verbindung zwischen der Ohrpathologie und einem Gerinnungsfaktorenmangel ist ein Hinweis, dass auf eine gestörte Hämostaseologie bei den betroffenen Kindern geachtet werden sollte. Weitere Arbeiten sind sowohl im Bereich der Therapie als auch der Prävention dieser Erkrankung notwendig, um die Behandlung dieser Kinder weiter zu optimieren.

Background To evaluate the immunogenicity of the inactivated herpes-zoster vaccine HZ/su in patients at increased risk for VZV-reactivation, we analysed the quantity and quality of the vaccine-induced cellular and humoral immunity in patients on dialysis with uremic immunodeficiency. Methods In this observational study, 29 patients and 39 immunocompetent controls underwent standard dual-dose vaccination. Blood samples were analysed before and two weeks after each vaccination, and after one year. Specific T-cells were characterized after stimulation with VZV-gE-peptides based on induction of cytokines and CTLA-4-expression using flow-cytometry. Antibodies were analysed using ELISA. Findings Both groups showed an increase in VZV-gE-specific CD4 T-cell levels over time (p < 0.0001), although median levels reached after second vaccination were lower in patients (0.17% (IQR 0.21%)) than in controls (0.24% (IQR 0.3%), p = 0.042). VZV-gE specific CD8 T-cells were only poorly induced. CTLA-4 expression on VZV-gE-specific CD4 T-cells was strongest after second dose with no differences between the groups (p = 0.45). Multifunctional cells co-expressing IFNγ, IL-2, and TNF were higher in patients after first vaccination (p = 0.028). Median VZV-specific IgG-levels reached a maximum after second vaccination with significantly lower levels in patients (10796 (IQR 12482) IU/l) than in controls (16899 (IQR 14019) IU/l, p = 0.009). Despite similar CD4 T-cell levels after one year (p = 0.415), antibody levels remained significantly lower in patients (p = 0.0008). Interpretation VZV-gE vaccination induced specific antibodies and CD4 T-cells in both patients and controls, whereas CD8 T-cell-induction was poor. Quantitative and qualitative differences in immunity may indicate reduced duration of protection which may necessitate booster vaccinations in patients on dialysis. Funding HOMFORexzellent (to D.S.).

Objective: Apheresis treatment (AT) is an established standard of treatment in various neurological autoimmune diseases. Since not all patients equally benefit from AT, we saw the need to investigate the effect of different clinical, paraclinical and technical-apparative factors on the clinical outcome. Additionally, we wanted to find out whether patients who improved due to AT continue to be clinically stable under B-cell depletion (BCD). Methods: We screened all patients (n = 358) with neurological diseases who received AT at the Medical center of the University of the Saarland in the past 20 years. Different factors (e.g., age, sex, duration until onset of AT, type of AT, number of cycles, csf parameters) were analyzed retrospectively. Clinical disability was measured using the modified Rankin scale (mRS), visual acuity and the Expanded Disability Status Scale (EDSS). Results: 335 patients, categorized into 11 different autoimmune diagnosis groups, received a total of 2669 treatment cycles and showed a statistically significant improvement in mRS with AT (p < 0.001). Patients in American Society for Apheresis (ASFA) categories I (p = 0.013) and II (p = 0.035) showed a significantly greater benefit under AT than those in category III. The clinical outcome was better with shorter duration until AT onset, more cycles of AT, and more plasma volume exchanged and the presence of an autoimmune antibody. Patients who initially profited had a significantly more stable course of the disease after 1-Year-BCD (p = 0.039). Discussion: In the present study, we were able to identify various significant factors influencing the outcome of patients due to AT. Furthermore, we could show that patients with a response to AT can benefit from BCD followup therapy.

Purpose:This study analyses the immune response of elite athletes after COVID-19 vaccination with double-dose mRNA and a single-dose vector vaccine. Methods:Immunoglobulin G (IgG) antibody titers, neutralizing activity, CD4 and CD8 T-cells were examined in blood samples from 72 athletes before and after vaccination against COVID-19 (56 mRNA (BNT162b2 / mRNA-1273), 16 vector (Ad26.COV.2) vaccines). Side effects and training time loss was also recorded. Results:Induction of IgG antibodies (mRNA : 5702 BAU/ml ; 4343 BAU/ml (hereafter: median), vector: 61 BAU/ml ; 52 BAU/ml, p<0.01), their neutralizing activity (99.7% ; 10.6%, p<0.01), and SARS-CoV-2 spike-specific CD4 T-cells (0.13% ; 0.05% ; p<0.01) after mRNA double-dose vaccines was significantly more pronounced than after a single-dose vector vaccine. SARS-CoV-2 spike-specific CD8 T-cell levels after a vector vaccine (0.15%) were significantly higher than after mRNA vaccines (0.02%; p<0.01). When athletes who had initially received the vector vaccine were boostered with an mRNA vaccine, IgG antibodies (to 3456 BAU/ml; p<0.01), neutralizing activity (to 100%; p<0.01), CD4 (to 0.13%; p<0.01) and CD8 T-cells (to 0.43%; p<0.01) significantly increased. When compared with dual-dose mRNA regimen, IgG antibody response was lower (p<0.01), the neutralizing activity (p<0.01) and CD8 T-cell (p<0.01) response higher and no significant difference in CD4 T-cell response (p=0.54) between the two regimens. Cumulative training loss (3 days) did not significantly differ between vaccination regimens (p=0.46). Conclusion:mRNA and vector vaccines against SARSCoV-2 appear to induce different patterns of immune response in athletes. Lower immune induction after a single-shot vector vaccine was clearly optimized by a heterologous booster. Vaccine reactions were mild and short-lived.

Knowledge is limited as to how prior SARS-CoV-2 infection influences cellular and humoral immunity after booster-vaccination with bivalent BA.4/5-adapted mRNA-vaccines, and whether vaccine-induced immunity may indicate subsequent infection. In this observational study, individuals with prior infection (n = 64) showed higher vaccine-induced anti-spike IgG-antibodies and neutralizing titers, but the relative increase was significantly higher in non-infected individuals (n = 63). In general, both groups showed higher neutralizing activity towards the parental strain than towards Omicron-subvariants BA.1, BA.2 and BA.5. In contrast, CD4 or CD8 T cell levels towards spike from the parental strain and the Omicron-subvariants, and cytokine expression profiles were similar irrespective of prior infection. Breakthrough infections occurred more frequently among previously non-infected individuals, who had significantly lower vaccine-induced spike-specific neutralizing activity and CD4 T cell levels. In summary, we show that immunogenicity after BA.4/5-bivalent vaccination differs between individuals with and without prior infection. Moreover, our results may help to improve prediction of breakthrough infections. Prior infection or exposure to SARS-CoV-2 may influence immunogenicity and effectiveness of subsequent vaccination to new strains of virus. Here the authors show that immunogenicity of a BA.4/5 mRNA vaccine differed in recipients depending on whether they had been exposed to or infected with an earlier strain of virus.

Knowledge on immunogenicity of the bivalent Omicron BA.4/5 vaccine in dialysis patients and the effect of a previous infection is limited. Therefore, vaccine-induced humoral and cellular immunity was analyzed in dialysis patients and immunocompetent controls with and without prior infection. In an observational study, 33 dialysis patients and 58 controls matched for age, sex and prior infection status were recruited. Specific IgG, neutralizing antibody activity and cellular immunity towards the spike-antigen from parental SARS-CoV-2 and Omicron-subvariants BA.1, BA.2 and BA.4/5 were analyzed before and 13-18 days after vaccination. The bivalent vaccine led to a significant induction of IgG, neutralizing titers, and specific CD4+ and CD8+ T-cell levels. Neutralizing activity towards the parental strain was higher than towards the Omicron-subvariants, whereas specific T-cell levels towards parental spike and Omicron-subvariants did not differ indicating substantial cross-reactivity. Dialysis patients with prior infection had significantly higher spike-specific CD4+ T-cell levels with lower CTLA-4 expression compared to infection-naive patients. When compared to controls, no differences were observed between infection-naive individuals. Among convalescent individuals, CD4+ T-cell levels were higher in patients and neutralizing antibodies were higher in controls. Vaccination was overall well tolerated in both dialysis patients and controls with significantly less adverse events among patients. In conclusion, our study did not provide any evidence for impaired immunogenicity of the bivalent Omicron BA.4/5 vaccine in dialysis patients. Unlike in controls, previous infection of patients was even associated with higher levels of spike-specific CD4+ T cells, which may reflect prolonged encounter with antigen during infection.