BackgroundIn hemodialysis patients, a third vaccination is frequently administered to augment protection against coronavirus disease 2019 (COVID-19). However, the newly emerged B.1.1.159 (Omicron) variant may evade vaccinal protection more easily than previous strains. It is of clinical interest to better understand the neutralizing activity against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants after booster vaccine or COVID-19 infection in these mostly immunocompromised patients.MethodsHemodialysis patients from four dialysis centers were recruited between June 2021 and February 2022. Each patient provided a median of six serum samples. SARS-CoV-2 neutralizing antibodies (nAbs) against wild type (WT) or Omicron were measured using the GenScript SARS-CoV-2 Surrogate Virus Neutralization Test Kit.ResultsForty-two patients had three doses of mRNA1273. Compared to levels prior to the third dose, nAb-WT increased 18-fold (peak at day 23) and nAb-Omicron increased 23-fold (peak at day 24) after the third dose. Peak nAb-WT exceeded peak nAb-Omicron 27-fold. Twenty-one patients had COVID-19 between December 24, 2021, and February 2, 2022. Following COVID-19, nAb-WT and nAb-Omicron increased 12- and 40-fold, respectively. While levels of vaccinal and post-COVID nAb-WT were comparable, post-COVID nAb-Omicron levels were 3.2 higher than the respective peak vaccinal nAb-Omicron. Four immunocompromised patients having reasons other than end-stage kidney disease have very low to no nAb after the third dose or COVID-19.ConclusionsOur results suggest that most hemodialysis patients have a strong humoral response to the third dose of vaccination and an even stronger post-COVID-19 humoral response. Nevertheless, nAb levels clearly decay over time. These findings may inform ongoing discussions regarding a fourth vaccination in hemodialysis patients.

Background To date it is unclear whether SARS-CoV-2 is present in spent dialysate from peritoneal dialysis (PD) patients with COVID-19. Our aim was to assess the presence or absence of SARS-CoV-2 in spent dialysate from chronic PD patients with confirmed diagnosis of COVID-19. Methods Spent PD dialysate samples from COVID-19 positive PD patients were collected between March and August 2020. The multiplexed real-time reverse transcriptase-polymerase chain reaction assay contained primer/probe sets specific to different SARS-CoV-2 genomic regions and to bacteriophage MS2 as internal process control for nucleic acid extraction. Demographic and clinical data were obtained from patients' electronic health records. Results A total of 26 spent PD dialysate samples were collected from 11 patients from 10 dialysis centers. Spent PD dialysate samples were collected on average 25±13 days (median 20, range 10 to 45) after onset of symptoms. The temporal distance of PD effluent collection relative to the closest positive nasal swab RT PCR was 15±11 days (median 14; range 1 to 41). All 26 PD effluent samples tested negative at three SARS-CoV-2 genomic regions. Conclusions Our findings indicate the absence of SARS-CoV-2 in spent PD dialysate collected 10 days or later after the onset of COVID-19 symptoms. We cannot rule out presence of SARS-CoV-2 in spent PD dialysate in the early stage of COVID-19.

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