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

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.