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

Abstract

<b><i>Introduction:</i></b> 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. <b><i>Methods:</i></b> 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. <b><i>Results:</i></b> 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 (<i>p</i> = 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; <i>p</i> = 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 (<i>p</i> = 0.24 and 0.56) but lower than healthy controls (<i>p</i> = 0.0013). <b><i>Conclusion:</i></b> 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.