Waning of SARS-CoV-2 Vaccine-Induced Immune Response over 6 Months in Peritoneal Dialysis Patients and the Role of a Booster Dose in Maintaining Seropositivity.

INTRODUCTION: Although lower than general population, newly developed SARS-CoV-2 vaccines generate immune responses in end-stage kidney disease patients. However, the persistence of immune responses in the long term is not known yet. This study aimed to evaluate humoral immune responses in peritoneal dialysis (PD) patients over 6 months and to analyze the effects of the booster dose. METHODS: Humoral immune responses of PD patients were measured after initial SARS-CoV-2 vaccinations and after 6 months following initial vaccinations. Immune responses were compared between patients who received and did not receive booster doses. PD patients were compared with 41 hemodialysis (HD) patients and 61 healthy controls. Humoral immune responses were measured by a commercial test that detects antibodies toward the receptor-binding domain of the spike protein of SARS-CoV-2. RESULTS: Twenty PD patients were evaluated over 6 months. The initial seropositivity rate was 90.9% with inactivated vaccine and 100% with mRNA vaccine. Seropositivity decreased to 44.4% after 6 months, and a booster dose helped in maintaining the 100% of seropositivity (p = 0.005). Magnitude of humoral response at the 6th month was also higher in patients who received the third dose (1,132.8 ± 769.6 AU/mL vs. 400.0 ± 294.6 AU/mL; p = 0.015). Among patients who did not receive the third dose, those who got mRNA vaccine could maintain higher seropositivity than others who got inactivated vaccine (75% vs. 40% for PD, 81.8% vs. 50% for HD). Seropositivity and antibody levels were similar for PD and HD patients after 6 months (p = 0.24 and 0.56) but lower than healthy controls (p = 0.0013). CONCLUSION: SARS-CoV-2 vaccine-induced antibody levels and seropositivity of PD patients significantly fall after 6 months. A booster dose after around 3 months following initial immunization might help in maintaining seropositivity.

Antibody responses to inactivated SARS-CoV-2 vaccine in peritoneal dialysis patients.

INTRODUCTION: As end-stage renal disease (ESRD) patients generally have reduced responses to the vaccines, effectiveness of newly developed SARS-CoV-2 vaccines in ESRD are also matters of curiosity. We aimed to investigate the humoral responses of our peritoneal dialysis (PD) patients to the inactivated SARS-CoV-2 vaccine. METHODS: Humoral immune responses of 23 PD patients who received two doses of the inactivated SARS-CoV-2 vaccine were investigated with a commercial test that measures IgG antibodies towards receptor binding domain of SARS-CoV-2 spike protein. Seropositivity rates, antibody titers, and ESRD related clinical data were compared with 51 hemodialysis (HD) patients and 29 healthy volunteers. RESULTS: Seropositivity of PD patients with the inactivated vaccine was 95.6%. Both the rate of seropositivity and SARS-CoV-2 IgG antibody levels in PD patients were not different from the healthy controls (p = 0.85 and 0.19, respectively). While seropositivity rates were not different for PD or HD patients (p = 0.09), the magnitude of humoral responses was significantly higher in PD patients (p = 0.0001). There were no vaccine-related serious adverse events. In the 3-months clinical follow-up, none of the patients experienced SARS-CoV-2 infection. CONCLUSION: Two doses of the inactivated vaccine generate adequate humoral immune response in PD patients without any serious adverse events.