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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.

BACKGROUND AND AIMS SARS-CoV-2 antibody titers after two doses of vaccination decrease over time. Hemodialysis patients are especially vulnerable to COVID-19 as they are immunocompromised, putting them at higher risk of infection and poorer response to vaccines. Therefore, administrating the third dose (‘booster’) in these patients is key to reduce COVID-19 infections and prevent severe illness. Dialysis patients were among the first group of patients who received booster vaccinations. To study the humoral response to the third injection in this group, we collected serum from 33 patients on hemodialysis and measured neutralizing antibody titers against SARS-CoV-2 before and after their booster doses. METHOD Patients were recruited from a dialysis center in New York City, NY from June to September 2021. Data on COVID-19 vaccination and demographics were collected upon enrollment. Blood samples were taken after enrollment. SARS-CoV-2 neutralization antibodies were assayed using the GenScript SARS-CoV-2 Surrogate Virus Neutralization Test Kit (Cat#L00847-A). Corresponding neutralizing antibody titers are presented as Unit/mL (U/mL). RESULTS A total of 33 in-center hemodialysis patients who had received three doses of vaccination were studied. Patients had a mean age of 61 years, 23 (70%) were male. Out of these, 31 (94%) patients received three doses of mRNA-1273 (Moderna), and two patients received the BNT162b2 (Pfizer BioNTech) vaccine. A total of 138 serum samples were analyzed (ranging from 156 days before to 85 days after the booster). Figure 1 shows the antibody titer distribution of all samples in these 33 patients. Each color indicates an individual patient. Each patient has up to 12 data points before and after the booster. The mean neutralizing antibody titers of all 48 data points pre-booster is 29.291 U/mL (range: 228–188.600). Seven days post-booster, the mean neutralizing antibody titer is 73.088 U/mL (range: 12.401–254.504). Mean titer is 169.826 U/mL (range: 17.830–375.046) at 14–28 days post-booster. After the peak time, we observe a decline of the titers. At 72–85 days, the mean titer is 72.179 (range: 33.702–204.382). We fitted a nonparametric mixed effects model with an adaptive spline and a random intercept for each subject to neutralizing antibody titers on the log10 scale. The estimate of the mean trajectory and its 95% confidence interval are shown in Fig. 2. The estimated peak time is 18.2 days with a 95% confidence interval (0–27.7). CONCLUSION Our results suggest that hemodialysis patients have a strong humoral response to booster vaccination. Neutralizing antibody titers peak at 18 days post-booster and wane to an average of 42% of peak value after 10–12 weeks.