Factors predictive of anti-spike antibody titers after COVID-19 vaccination in hemodialysis patients

Abstract

Hemodialysis (HD) patients have a high prevalence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and mortality, but they may have a weak response to coronavirus disease 2019 (COVID-19) vaccines. This study aimed to evaluate factors predictive of humoral response in HD patients vaccinated against SARS-CoV-2 infection. This is a 2-center observational study including HD patients who received the BNT162b2 mRNA vaccine followed by serological measurements 20 days and 4 weeks after the 1st and 2nd dose, respectively. Healthy controls were included. Anti-spike antibody was measured using the chemiluminescent immunoassay (CLIA) method. The quantile regression analysis was performed to assess factors associated with anti-spike antibody titers. Seventy-two HD patients and 22 healthy controls were included. Mean age of dialysis patients and controls was 72.5 ±11.5 years and 45.7 ±17.4 years, respectively. In the HD group, median levels of anti-spike antibody were 3 (interquartile range (IQR): 0.5-26) UI/mL and 391 (IQR: 55-1642) UI/mL after the 1st and 2nd dose, respectively, with response rates of 62.5% and 96.7%. The median level of the anti-spike antibody after the 1st dose in previously infected patients was 8571 (IQR: 2586-19147) UI/mL. There was a significant correlation between anti-spike antibody levels after the 2nd dose and age and anti-hepatitis B surface (HBs) antibody and serum albumin levels (Spearman's rho: r = -0.289, p < 0.001; r = 0.357, p = 0.027; r = 0.317; p = 0.026, respectively). The regression analysis showed a significant association of previous infection and anti-Hbs antibody level with anti-spike antibody level after the 1st dose of vaccine (p < 0.001). After a 5-month follow-up, 2 vaccinated patients contracted COVID-19. This study showed a response rate of 96.7% to 2 doses of BNT162b2 mRNA vaccine in HD patients and 100% to a single dose in previously infected patients. The level of anti-spike antibody can be predicted by age, anti-Hbs antibodies, serum albumin, and previous infection. Despite the immunization of patients, preventive measures should be maintained in all dialysis units.