Background:Dialysis patients have a higher COVID-19 fatality rate than the general population and are priority candidates for SARS-CoV-2 vaccination. However, dialysis patients are immunocompromised, suggesting that they may develop a less immune response to COVID-19 vaccination than healthy individuals.Objective and Methods:A total of 358 hemodialysis patients who were twice-vaccinated with BNT162b2 were included. SARS-CoV-2 IgG antibody titer was measured within 7 days to 1 month, 1∼2 months, and 3∼4 months after the second vaccination, and factors influencing antibody titer were statistically investigated. SARS-CoV-2 IgG measurement was performed using SARS-CoV-2 IgG II Quant Reagent (Abbott), which is a reagent to quantitatively measure IgG antibodies against the receptor-binding domain of SARS-CoV-2 spike protein.Results:The patients were 240 males (67%) and 118 females, ranging from 37 to 95 years old, with a median age of 70 years. Causes of kidney failure were diabetes mellitus in 35.2%, hypertensive kidney disease in 7.3%, glomerular disease in 30.5%, and polycystic kidney disease in 4.5% of the patients. Comorbidities were hypertension in 64.3% and diabetes in 48.9%. Steroids or immunosuppressive drugs were used in 9% of the patients. SARS-CoV-2 IgG antibody titers at 7 days to 1 month, 1 to 2 months, and 3 to 4 months (median 10, 42, and 98 days) after the second vaccination have the median of 4092 AU/mL(with interquartile range: 1354, 7592), 2199 (927, 4692), and 789 (323, 1559), respectively. Post-vaccination SARS-CoV-2 IgG titers were significantly correlated with Kt/V, the presence of autoimmune diseases, the use of steroids or immunosuppressive drugs, malignancy treatment, and serum albumin and hemoglobin levels. Multivariate analysis showed that the factors that decreased post-vaccination SARS-CoV-2 IgG titer were the use of steroids and immunosuppressive drugs, the presence of malignant tumors under treatment, and hypoalbuminemia.Conclusion:Compared to healthy subjects in previous reports, dialysis patients had lower SARS-CoV-2 IgG titers after COVID-19 vaccination, suggesting that the vaccine may not be sufficiently effective. In addition, SARS-CoV-2 IgG titers are likely to be even lower in patients at high risk for decreased immune response due to medications or comorbidities. Additional vaccination may be essential for hemodialysis patients who are expected to have low SARS-CoV-2 IgG titers.