Longitudinal SARS-CoV-2 neutralization of Omicron BA.1, BA.5 and BQ.1.1 after four vaccinations and the impact of breakthrough infections in haemodialysis patients

Background Individuals on hemodialysis are more vulnerable to SARS-CoV-2 infection than the general population due to end-stage kidney disease-induced immunosuppression. Methods 26 hemodialysis patients experiencing SARS-CoV-2 infection after 3rd vaccination were matched 1:1 to 26 out of 92 SARS-CoV-2 naives by age, sex, dialysis vintage and immunosuppressive drugs receiving a 4th vaccination with an mRNA-based vaccine. A competitive surrogate neutralization assay was used to monitor vaccination success. To determine infection neutralization titers, Vero-E6 cells were infected with SARS-CoV-2 variants of concern (VoC), Omicron sub-lineage BA.1, BA.5, and BQ.1.1. 50% inhibitory concentration (IC50, serum dilution factor 1:x) was determined before, four weeks after and 6 months after the 4th vaccination. Results 52 hemodialysis patients received four COVID-19 vaccinations and were followed up for a median of 6.3 months. Patient characteristics did not differ between the matched cohorts. Patients without a SARS-CoV-2 infection had a significant reduction of real virus neutralization capacity for all Omicron sub-lineages after six months (p<0.001 each). Those patients with a virus infection did not experience a reduction of real virus neutralization capacity after six months. Compared to the other Omicron VoC the BQ.1.1 sub-lineage had the lowest virus neutralization capacity. Conclusions SARS-CoV-2-naive hemodialysis patients had significantly decreased virus neutralization capacity six months after the 4th vaccination whereas patients with a SARS-CoV-2 infection had no change in neutralization capacity. This was independent of age, sex, dialysis vintage and immunosuppression. Therefore, in infection-naive hemodialysis patients a fifth COVID-19 vaccination might be reasonable 6 months after the 4th vaccination.