Hemodialysis patients are exposed to a markedly increased risk when infected with SARS-CoV-2. To date, it is unclear if hemodialysis patients benefit from four vaccinations. A total of 142 hemodialysis patients received four COVID-19 vaccinations until March 2022. RDB binding antibody titers were determined in a competitive surrogate neutralization assay. Vero-E6 cells were infected with SARS-CoV-2 variants of concern (VoC), Delta (B.1.617.2), or Omicron (B.1.1.529, sub-lineage BA.1) to determine serum infection neutralization capacity. Four weeks after the fourth vaccination, serum infection neutralization capacity significantly increased from a 50% inhibitory concentration (IC50, serum dilution factor 1:x) of 247.0 (46.3–1560.8) to 2560.0 (1174.0–2560.0) for the Delta VoC, and from 37.5 (20.0–198.8) to 668.5 (182.2–2560.0) for the Omicron VoC (each p < 0.001) compared to four months after the third vaccination. A significant increase in the neutralization capacity was even observed for patients with high antibody titers after three vaccinations (p < 0.001). Ten patients with SARS-CoV-2 breakthrough infection after the first blood sampling had by trend lower prior neutralization capacity for Omicron (p = 0.051). Our findings suggest that hemodialysis patients benefit from a fourth vaccination in particular in the light of the highly infectious SARS-CoV-2 Omicron-variants. A routinely applied four-time vaccination seems to broaden immunity against variants and would be recommended in hemodialysis patients.

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Background Hemodialysis patients are exposed to a markedly increased risk when infected with SARS-CoV-2. To date it is unclear if hemodialysis patients benefit from a fourth vaccination. Methods A total of 142 hemodialysis patients (median age 72.6 years, 33.8% female) received four COVID-19 vaccinations between December 2020 and March 2022. RDB binding antibody titers were determined in a competitive surrogate neutralization assay. Vero-E6 cells were infected with SARS-CoV-2 variants of concern (VoC) Delta (B.1.617.2) or Omicron (B.1.1.529, sub lineage BA.1) in a biosafety level 3 laboratory to determine serum infection neutralization capacity before and after vaccination. Results After the fourth vaccination serum infection neutralization capacity significantly increased from a 50% inhibitory concentration (IC50, serum dilution factor 1:x) of 247.0 (46.3-1560.8) to 2560.0 (1174.0-2560.0) for the Delta VoC, and from 37.5 (20.0-198.8) to 668.5 (182.2-2560.0) for the Omicron VoC (each p<0.001). A significant increase of the neutralization capacity was even observed for patients who had high antibody titers after three vaccinations (p<0.001). Univariate regression analysis indicated immunosuppressive medication (p=0.001) and hepatitis B vaccination non-response (p=0.046), and multivariate analysis immunosuppressive medication as the only factor associated with a reduced effect against Delta (p<0.001). Ten patients with SARS-CoV-2 breakthrough infection before the fourth vaccination had by trend lower prior neutralization capacity for Omicron (p=0.051). Conclusions Our findings suggest that hemodialysis patients benefit from a fourth vaccination in particular in the light of the highly infectious SARS-CoV-2 Omicron variant. A routinely applied four-time vaccination seems to broaden immunity against variants and would be recommended in hemodialysis 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 naïves 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 &lt; 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-naïve 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-naïve hemodialysis patients a fifth COVID-19 vaccination might be reasonable 6 months after the 4th vaccination.