Comparison of antibody response following the second dose of SARS-CoV-2 mRNA vaccine in elderly patients with late-stage chronic kidney disease

Background: Currently, it is unclear whether the progression of chronic kidney disease (CKD) could be an independent predictor of antibody response after administration of a COVID-19 vaccine. This study aimed to investigate the immune response to COVID-19 vaccination in patients with CKD stage G4 to G5 without renal replacement therapy and G5D using the recommended dose and schedule. Methods: This retrospective single-center cohort study evaluated immunogenicity regarding antibody response after COVID-19 vaccination in our hospital for late-stage CKD patients aged ≥ 60 years. We evaluated antibody responses in 48 patients with CKD G4, 35 patients with CKD G5, and 70 patients undergoing hemodialysis (HD; CKD G5D). Results: After the second vaccination, anti-SARS-CoV-2-S (Spike) IgG levels were found to be positive (> 0.8 U/mL) in all CKD G4 and G5 patients (100%), and 69 of 70 HD patients (98.5%). The median (interquartile range [IQR] S-IgG level (Ab titers) was 358 [130.2–639.2], 218 [117–377], and 185.5 [95.1–323.5] U/mL in the CKD G4, G5, and HD groups, respectively. The median S-IgG levels were significantly lower in the HD group than in the CKD G4 group (p < 0.01). However, there was no significant difference in the antibody titers between the CKD G4 and G5 groups. To further analyze the decline in S-IgG levels after 6 months, we additionally assessed and compared antibody titers at 1 month and 6 months after the second vaccination in the HD group. Compared with the median S-IgG levels of 185.5 [95.1–323.5] U/mL 1 month after the second dose, the median S-IgG level 6 months thereafter was significantly decreased at 97.4 [62.5–205.5] U/mL (p < 0.05). Conclusions: We highlight two major factors of variability in the vaccine response. First, in elderly patients with late-stage CKD, antibody titers tended to be lower in the G5D group than in the G4 and G5 groups despite the shorter time since vaccination; therefore, CKD stage progression might cause a decline in antibody titers. Second, waning immune responses were observed 6 months after second dose administration in HD patients advocating a potential need for a third booster dose vaccine after 6 months.