SARS-CoV-2-specific immunity after XBB.1.5 vaccination is not influenced by subsequent influenza vaccination in dialysis patients

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.