Supplementary Material for: Humoral Response to the Third Dose of BNT162b2 COVID-19 Vaccine among Hemodialysis Patients

Background: Hemodialysis patients are at high risk for severe COVID-19 disease. Despite a high early seropositivity rate, dialysis patients mount a dampened immune response following two doses of an mRNA vaccine. This study aimed to evaluate the serologic response to a booster dose of BNT162b2 vaccine, 6 months after the second dose, among hemodialysis patients. Methods: This prospective study included 80 hemodialysis patients and 56 healthcare workers serving as controls. Serologic samples were evaluated before and ∼3 weeks after the third vaccine dose. The primary outcomes were the seropositivity rate and the log-transformed anti-SARS-COV-2 S1 (RBD) IgG as a continuous variable after the third dose. Secondary outcomes were the proportion of participants with “high response,” defined as antibody levels >1,000 AU/mL, and “robust response,” defined as antibody levels >4,160 AU/mL, according to prespecified cutoff values associated with neutralizing antibodies. Univariate and multivariate analyses were conducted to identify predictors of antibody response. Results: Among 80 hemodialysis patients, seropositivity rates improved from 78% (62/80) before the third dose, up to 96% (77/80) after the booster dose. The S1-RBD log-transformed antibody level increased significantly following the third dose from 2.15 ± 0.75 to 3.99 ± 0.83 compared with 2.65 ± 0.4 to 4.31 ± 0.42 in the control group. Among the hemodialysis patients, 88% (70/80) became “high responders” (>1,000 AU/mL), and of these, 79% (63/80) mounted a “robust response” (>4,160 AU/mL). Baseline antibody level, dialysis therapy, and hypoalbuminemia were independent predictors of impaired antibody response. Conclusions: A third dose of BNT162b2 COVID-19 vaccine, 6 months after the standard two-dose vaccination regimen, substantially improved humoral response in hemodialysis patients.背景：血液透析患者罹患重症新型冠状病毒肺炎（COVID-19）的风险极高。尽管早期血清阳转率较高，但血液透析患者在接种两剂mRNA疫苗后，免疫应答会出现减弱。本研究旨在评估血液透析患者在完成两剂标准接种6个月后，接种BNT162b2疫苗加强针后的血清学应答情况。 方法：本前瞻性研究纳入80名血液透析患者及56名作为对照的医护人员。分别于第三剂疫苗接种前及接种后约3周采集血清样本进行检测。主要结局指标为第三剂接种后的血清阳转率，以及以连续变量形式呈现的经对数转换的抗严重急性呼吸综合征冠状病毒2（SARS-CoV-2）S1（受体结合域，RBD）IgG水平。次要结局指标为根据预先设定的与中和抗体相关的截断值划分的“高应答者”（抗体水平＞1000 AU/mL）和“强应答者”（抗体水平＞4160 AU/mL）的受试者占比。采用单因素及多因素分析筛选抗体应答的影响因素。 结果：80名血液透析患者中，第三剂接种前血清阳转率为78%（62/80），加强针接种后升至96%（77/80）。S1-RBD经对数转换的抗体水平在第三剂接种后显著升高，血液透析患者组从2.15±0.75升至3.99±0.83，对照组则从2.65±0.4升至4.31±0.42。血液透析患者中，88%（70/80）成为“高应答者”（＞1000 AU/mL），其中79%（63/80）达到“强应答”标准（＞4160 AU/mL）。基线抗体水平、透析治疗及低白蛋白血症是抗体应答受损的独立影响因素。 结论：在标准两剂接种方案完成6个月后接种第三剂BNT162b2新型冠状病毒肺炎疫苗，可显著改善血液透析患者的体液免疫应答。