Longitudinal cellular and humoral immune responses after triple BNT162b2 and fourth full-dose mRNA-1273 vaccination in haemodialysis patients

Background Haemodialysis patients are at-risk for severe COVID-19 and were among the first to receive a fourth COVID-19 vaccination. Methods We analysed humoral responses by multiplex-based IgG measurements against the receptor-binding domain (RBD) and ACE2-binding inhibition towards variants of concern including Omicron in haemodialysis patients and controls after triple BNT162b2 vaccination and in dialysis patients after a fourth full-dose of mRNA-1273. T-cell responses were assessed by interferon γ release assay. Findings After triple BNT162b2 vaccination, anti-RBD B.1 IgG and ACE2 binding inhibition reached peak levels in dialysis patients, but remained inferior compared to controls. Whilst we detected B.1-specific ACE2 binding inhibition in 84% of dialysis patients after three BNT162b2 doses, binding inhibition towards the Omicron variant was only 38% and declining to 16% before the fourth vaccination. By using mRNA-1273 as fourth dose, humoral immunity against all SARS-CoV-2 variants tested was strongly augmented with 80% of dialysis patients having Omicron-specific ACE2 binding inhibition. Modest declines in T-cell responses in dialysis patients and controls after the second vaccination were restored by the third BNT162b2 dose and significantly increased by the fourth vaccination. Conclusions A fourth full-dose mRNA-1273 after triple BNT162b2 vaccination in haemodialysis patients leads to efficient humoral responses against Omicron. Our data support current national recommendation and suggest that other immune-impaired individuals may benefit from this mixed mRNA vaccination regimen. Funding Initiative and Networking Fund of the Helmholtz Association of German Research Centres, EU Horizon 2020 research and innovation program, State Ministry of Baden-Württemberg for Economic Affairs, Labour and Tourism, European Regional Development Fund Research in the context Evidence before this study Information on how to best maintain immune protection after SARS-CoV-2 vaccination in at-risk individuals for severe COVID-19 such as haemodialysis patients is limited. We searched PubMed and medRxiv for keywords such as “haemodialysis”, “SARS-CoV-2”, “vaccine”, “decay”, “antibody kinetics”, “cellular immunity”, “longitudinal vaccination response”, “immunisation scheme”. To date, no peer-reviewed studies comprehensively assessed impact of both cellular and humoral immunogenicity after a triple BNT162b2 vaccination in combination with a fourth full-dose of mRNA-1273 and addressed the impact of currently dominating SARS-CoV-2 variants of concern on vaccine-induced immunity in this at-risk population. Added value of the study We provide to the best of our knowledge for the first time longitudinal vaccination response data over the course of the pandemic in dialysis patients. We studied not only systemic T- and B-cell but also mucosal responses in this at-risk group and determined levels of neutralizing antibodies towards Omicron BA.1 and Delta variants after a mixed mRNA vaccine schedule. Implications of all the available evidence Patients on haemodialysis show inferior response rates and thus a more rapid decline in humoral immune response after triple vaccination with BNT162b2. Our data strongly support the concept of administering a fourth full-dose of mRNA-1273 as part of a heterologous vaccination scheme to boost immunity and to prevent severe COVID-19 within this at-risk population. Strategic application of modified vaccine regimens may be an immediate response against SARS-CoV-2 variants with increased immune evasion potential.