Anti-SARS-CoV-2 spike antibody response to the third dose of BNT162b2 mRNA COVID-19 vaccine and associated factors in Japanese hemodialysis patients

Keiji Hirai; Masako Shimotashiro; Toshiaki Okumura; Susumu Ookawara; Yoshiyuki Morishita

doi:10.23876/j.krcp.23.121

Kidney Res Clin Pract > Volume 43(3); 2024 > Article

Hirai, Shimotashiro, Okumura, Ookawara, and Morishita: Anti-SARS-CoV-2 spike antibody response to the third dose of BNT162b2 mRNA COVID-19 vaccine and associated factors in Japanese hemodialysis patients

Original Article

Kidney Research and Clinical Practice 2024;43(3):326-336.

Published online: February 19, 2024

DOI: https://doi.org/10.23876/j.krcp.23.121

Anti-SARS-CoV-2 spike antibody response to the third dose of BNT162b2 mRNA COVID-19 vaccine and associated factors in Japanese hemodialysis patients

Keiji Hirai¹

, Masako Shimotashiro²

, Toshiaki Okumura²

, Susumu Ookawara¹

, Yoshiyuki Morishita¹

¹Division of Nephrology, First Department of Integrated Medicine, Saitama Medical Center, Jichi Medical University, Saitama, Japan

²Mizue Yuai Clinic, Tokyo, Japan

Correspondence: Keiji Hirai Division of Nephrology, First Department of Integrated Medicine, Saitama Medical Center, Jichi Medical University, 1-847 Amanuma-cho, Omiya-ku, Saitama-shi, Saitama-ken 330-8503, Japan. E-mail: keijihirai@kfy.biglobe.ne.jp

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial and No Derivatives License (http://creativecommons.org/licenses/by-nc-nd/4.0/) which permits unrestricted non-commercial use, distribution of the material without any modifications, and reproduction in any medium, provided the original works properly cited.

Abstract

Background

We assessed the anti-SARS-CoV-2 spike antibody response to the third dose of BNT162b2 mRNA COVID-19 vaccine in Japanese hemodialysis patients and determined factors associated with the anti-SARS-CoV-2 spike antibody titer after the third dose of COVID-19 vaccine.

Methods

Overall, 64 patients were enrolled in this single-center, prospective, longitudinal study. Anti-SARS-CoV-2 spike antibody titers were compared between hemodialysis patients and 18 healthcare workers. Multiple linear regression analysis was used to identify factors associated with the anti-SARS-CoV-2 spike antibody titer after the third vaccination.

Results

There was no significant difference in anti-SARS-CoV-2 spike antibody titer 4 weeks after the third vaccination between hemodialysis patients and healthcare workers (18,500 [interquartile range, 11,000–34,500] vs. 11,500 [interquartile range, 7,918–19,500], all values in AU/mL; p = 0.17). Uric acid (standard coefficient [β] = −0.203, p = 0.02), transferrin saturation (β = −0.269, p = 0.003), and log–anti-SARS-CoV-2 spike antibody titer 1 week before the third vaccination (β = 0.440, p < 0.001) correlated with the log–anti-SARS-CoV-2 spike antibody titer 4 weeks after the third vaccination. In contrast, only the log–anti-SARS-CoV-2 spike antibody titer 1 week before the third vaccination (β = 0.410, p < 0.001) correlated with the log–anti-SARS-CoV-2 spike antibody titer 12 weeks after the third vaccination.

Conclusion

The anti-SARS-CoV-2 spike antibody titer after the third dose of COVID-19 vaccine was comparable between hemodialysis patients and healthcare workers. Uric acid concentration, transferrin saturation, and anti-SARS-CoV-2 spike antibody titer before the third dose were associated with the anti-SARS-CoV-2 spike antibody titer after the third dose in Japanese hemodialysis patients.

Keywords: BNT162 vaccine, COVID-19, Hemodialysis, SARS-CoV-2

Graphical abstract

Introduction

Hemodialysis patients are one of the most vulnerable populations at risk for severe and fatal coronavirus disease 2019 (COVID-19) [1]. COVID-19 vaccination was reported to reduce the risk of hospitalization and death associated with COVID-19 in hemodialysis patients [2], and its preventable effects were associated with the anti-severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike antibody titer after COVID-19 vaccination [3]. Therefore, maintaining an adequate anti-SARS-CoV-2 spike antibody titer is important to prevent severe COVID-19 and COVID-19-related deaths in hemodialysis patients.

Recently, several studies have investigated the anti-SARS-CoV-2 spike antibody response to the third dose of COVID-19 vaccine in patients undergoing hemodialysis [4,5]. An observational study reported that the anti-SARS-CoV-2 spike antibody titer after the third dose of COVID-19 vaccine was lower in hemodialysis patients compared with that in healthcare workers [4]. Another observational study reported that the anti-SARS-CoV-2 spike antibody titer in hemodialysis patients after the third dose of COVID-19 vaccine was similar to that of healthcare workers [5]. Recent studies also revealed that the anti-SARS-CoV-2 spike antibody level before the third COVID-19 vaccination, immunosuppressive medication, and hypoalbuminemia were associated with the anti-SARS-CoV-2 spike antibody response after the third COVID-19 vaccination in patients undergoing hemodialysis [4,6,7]. However, factors associated with the anti-SARS-CoV-2 spike antibody response to the third COVID-19 vaccination have not been investigated in Asian individuals undergoing hemodialysis. Therefore, in the present study, we determined which clinical factors were associated with the anti-SARS-CoV-2 spike antibody titer after the third dose of COVID-19 vaccine in Japanese patients undergoing hemodialysis. We also assessed the anti-SARS-CoV-2 spike antibody titers in hemodialysis patients before and after the third dose of COVID-19 vaccine and compared it with that in healthcare workers.

Methods

Ethical approval

The Ethical Committee of Mizue Yuai Clinic approved this study (No. MYC 2021-01), which was performed in accordance with the Declaration of Helsinki. Written informed consent was obtained from all study participants.

Patients

The study inclusion criteria were: 1) age, ≥20 years; 2) currently receiving maintenance hemodialysis; and 3) vaccinated with two doses of BNT162b2 messenger RNA (mRNA) COVID-19 vaccine (Pfizer Inc. and BioNTech) with a dose interval of 3 weeks between the ﬁrst and second doses and scheduled to receive the third dose with a dose interval of 24 weeks between the second and third doses. The following exclusion criteria were applied: 1) unable or unwilling to give consent and 2) any history of COVID-19 infection. Healthcare workers who were vaccinated three times with the BNT162b2 mRNA COVID-19 vaccine and consented to participate were used as the control group.

Study design

This was a single-center, prospective, longitudinal study conducted between April 1, 2021 and June 30, 2022 at the Mizue Yuai Clinic in Tokyo. Fig. 1 illustrates the study flow chart. Each participant’s anti-SARS-CoV-2 spike antibody titer was measured 1 week before and 4 and 12 weeks after the third dose of the BNT162b2 mRNA COVID-19 vaccine. Clinical and demographic parameters were collected during the week when the third BNT162b2 mRNA COVID-19 vaccine was administered. We assessed the change in anti-SARS-CoV-2 spike antibody titers in hemodialysis patients between 1 week before and 12 weeks after the third BNT162b2 mRNA COVID-19 vaccination. We compared the anti-SARS-CoV-2 spike antibody titers between healthcare workers (control group) and hemodialysis patients (hemodialysis patient group) 1 week before and 4 weeks after the third dose of the BNT162b2 mRNA COVID-19 vaccine. We also conducted a multiple linear regression analysis to identify factors associated with the anti-SARS-CoV-2 spike antibody titers in hemodialysis patients 4 weeks and 12 weeks after the third BNT162b2 mRNA COVID-19 vaccination. Based on a previous report [5], we divided hemodialysis patients into three categories according to their anti-SARS-CoV-2 spike antibody response status 4 weeks after the third BNT162b2 mRNA COVID-19 vaccination (no, low, and high responder) and compared their clinical and demographic parameters.

Laboratory methods

Hemodialysis patients’ blood samples were obtained using an arteriovenous fistula immediately before the start of their first hemodialysis session of the week. A commercial laboratory (BML) measured the patients’ anti-SARS-CoV-2 spike antibody titers and blood parameters. The SARS-CoV-2 IgG II Quant immunoassay (Abbott) was used to determine anti-SARS-CoV-2 spike antibody titers. Shinzato et al.’s formula [8] was used to calculate the single-pool urea clearance and normalized protein catabolism rate.

Statistical analyses

Data of continuous variables are shown as the mean ± standard deviation when they are normally distributed. Data that were not normally distributed are shown as the median (interquartile range [IQR]). Data of categorical variables are presented as numbers and percentages. The hemodialysis vintage, C-reactive protein, ferritin, and anti-SARS-CoV-2 spike antibody titers including that 1 week before the third BNT162b2 mRNA COVID-19 vaccination did not show normal distributions; therefore, these variables were transformed using the natural logarithm. The Friedman test and the Steel-Dwass test were conducted to compare the anti-SARS-CoV-2 spike antibody titers within each group. Comparisons of anti-SARS-CoV-2 spike antibody titers between healthcare workers and hemodialysis patients were conducted using the Mann-Whitney U test. Comparisons of clinical and demographic parameters between the two groups were conducted using the Student t test for continuous variables and Fisher’s exact test for categorical variables. Comparisons of clinical and demographic parameters among the three groups were conducted using the Kruskal-Wallis test with the Steel-Dwass test for continuous variables and the Fisher exact test with Bonferroni correction for categorical variables. Simple linear regression analyses were performed with the anti-SARS-CoV-2 spike antibody titers 4 weeks and 12 weeks after the third BNT162b2 mRNA COVID-19 vaccination as dependent variables and with clinical and demographic parameters including the anti-SARS-CoV-2 spike antibody titer 1 week before the third BNT162b2 mRNA COVID-19 vaccination as independent variables. In a multiple linear regression analysis, we included the parameters that appeared to be correlated significantly with the anti-SARS-CoV-2 spike antibody titers 4 weeks and 12 weeks after the third BNT162b2 mRNA COVID-19 vaccination in the simple linear regression analyses (p < 0.10), to identify which variables were independently correlated with the anti-SARS-CoV-2 spike antibody titers 4 weeks and 12 weeks after the third BNT162b2 mRNA COVID-19 vaccination. The p-values of <0.05 were considered statistically significant. All statistical analyses were conducted using JMP version 11 (SAS Institute).

Results

Patient characteristics

All the patients undergoing hemodialysis in our center during the study period were screened for study entry. Of these, eight were unwilling or unable to give consent, and the remaining 75 hemodialysis patients were enrolled in this study. A total of 22 healthcare workers were enrolled as controls. Of the hemodialysis patients, 10 developed COVID-19 infection and one changed to another hospital. Therefore, the hemodialysis patient group was comprised of 64 patients. Blood samples were not available for four healthcare workers and the control group was comprised of 18 healthcare workers. Therefore, we analyzed the data of 64 hemodialysis patients and 18 healthcare workers (Fig. 1). Table 1 summarizes the patient characteristics and medications of both groups. Hemodialysis patients’ laboratory data were obtained at the start of their first hemodialysis session of the week when the third BNT162b2 mRNA COVID-19 vaccine was administered. Healthcare workers’ laboratory data were obtained at the time of the third BNT162b2 mRNA COVID-19 vaccination.

The hemodialysis patient group consisted of 37 male and 27 female patients, with a mean age of 71.4 ± 11.7 years, body mass index (BMI) of 21.9 ± 3.9 kg/m², and hemodialysis vintage of 4.5 years (IQR, 2.0–9.0 years). Twelve patients (18.8%) had a history of past or current smoking and 11 patients (17.2%) had a habit of alcohol consumption. The proportions of patients with hypertension, diabetes mellitus, autoimmune diseases, and allergic diseases were 60.9%, 43.8%, 9.4%, and 29.7%, respectively. The percentages of patients with a history of infection were as follows: hepatitis B virus, 17.2%; hepatitis C virus, 3.1%; and syphilis, 6.3%. The control group included 18 healthcare workers (8 males, 10 females; mean age, 45.9 ± 12.2 years; BMI, 24.8 ± 5.8 kg/m²). Seven healthcare workers (38.9%) had a history of past or current smoking and 11 (61.1%) had a habit of alcohol consumption. The percentages of healthcare workers with hypertension, diabetes mellitus, autoimmune diseases, and allergic diseases were 16.7%, 5.6%, 0.0%, and 27.8%, respectively. No healthcare workers had a history of hepatitis B virus, hepatitis C virus, or syphilis infections. Medication use among hemodialysis patients was as follows: renin-angiotensin system inhibitors, 37.5%; antihyperuricemic drugs, 21.9%; statins, 31.3%; erythropoiesis-stimulating agents, 87.5%; hypoxia-inducible factor prolyl hydroxylase inhibitors, 6.3%; iron supplements, 63.5%; zinc supplements, 10.9%; phosphate binders, 79.7%; vitamin D analogs, 84.4%; calcimimetics, 37.5%; and corticosteroids, 4.7%. The proportions of healthcare workers taking each medication were: renin-angiotensin system inhibitors, 11.1%; antihyperuricemic drugs, 22.2%; and statins, 5.6%.

Change in anti-SARS-CoV-2 spike antibody titers in hemodialysis patients

As shown in Fig. 2, the anti-SARS-CoV-2 spike antibody titer was significantly increased from 220 AU/mL (IQR, 134–419 AU/mL) 1 week before the third BNT162b2 mRNA COVID-19 vaccination to 18,500 AU/mL (IQR, 11,000–34,500 AU/mL) 4 weeks after the third BNT162b2 mRNA COVID-19 vaccination (p < 0.001). Thereafter, it decreased significantly to 10,355 AU/mL (IQR, 4,584–22,250 AU/mL) 12 weeks after the third BNT162b2 mRNA COVID-19 vaccination (p < 0.001); however, it was still significantly higher than at 1 week before the third BNT162b2 mRNA COVID-19 vaccination (p < 0.001).

Comparison of anti-SARS-CoV-2 spike antibody titers between the control and hemodialysis patient groups

The anti-SARS-CoV-2 spike antibody titer 1 week before the third BNT162b2 mRNA COVID-19 vaccination was significantly lower in hemodialysis patients than in healthcare workers (220 AU/mL [IQR, 134–419 AU/mL] vs. 2,626 AU/mL [IQR, 1,869–5,730 AU/mL], p < 0.001) (Fig. 2). However, there was no significant difference between the two groups 4 weeks after the third BNT162b2 mRNA COVID-19 vaccination (18,500 AU/mL [IQR, 11,000–34,500 AU/mL] vs. 11,500 AU/mL [IQR, 7,918–19,500 AU/mL], p = 0.17).

Factors associated with the anti-SARS-CoV-2 spike antibody titer after the third BNT162b2 mRNA COVID-19 vaccination

According to the simple linear regression analyses, the log–anti-SARS-CoV-2 spike antibody titer 4 weeks after the third BNT162b2 mRNA COVID-19 vaccination correlated significantly with the BMI, presence of diabetes mellitus, blood urea nitrogen, total calcium, uric acid, transferrin saturation (TSAT), normalized protein catabolism rate, and log–anti-SARS-CoV-2 spike antibody titer 1 week before the third BNT162b2 mRNA COVID-19 vaccination (Table 2). In contrast, the log–anti-SARS-CoV-2 spike antibody titer 12 weeks after the third BNT162b2 mRNA COVID-19 vaccination correlated significantly with the presence of diabetes mellitus, blood urea nitrogen, uric acid, total cholesterol, TSAT, normalized protein catabolism rate, and log–anti-SARS-CoV-2 spike antibody titer 1 week before the third BNT162b2 mRNA COVID-19 vaccination (Table 3). We then conducted multiple linear regression analyses using the variables that showed significant or marginal correlations (p < 0.10) with the log–anti-SARS-CoV-2 spike antibody titers 4 and 12 weeks after the third BNT162b2 mRNA COVID-19 vaccination in the simple linear regression analyses. These analyses revealed that uric acid (standard coefficient [β] = −0.203, p = 0.02), TSAT (β = −0.269, p = 0.003), and log–anti-SARS-CoV-2 spike antibody titer 1 week before the third BNT162b2 mRNA COVID-19 vaccination (β = 0.440, p < 0.001) were correlated independently with the log–anti-SARS-CoV-2 spike antibody titer 4 weeks after the third BNT162b2 mRNA COVID-19 vaccination (Table 2). In contrast, only the log–anti-SARS-CoV-2 spike antibody titer 1 week before the third BNT162b2 mRNA COVID-19 vaccination (β = 0.410, p < 0.001) correlated independently with the log–anti-SARS-CoV-2 spike antibody titer 12 weeks after the third BNT162b2 mRNA COVID-19 vaccination (Table 3).

Patient characteristics categorized by the anti-SARS-CoV-2 spike antibody response status 4 weeks after the third BNT162b2 mRNA COVID-19 vaccination

Patient characteristics categorized by the anti-SARS-CoV-2 spike antibody response status 4 weeks after the third BNT162b2 mRNA COVID-19 vaccination are shown in Table 4. The number of hemodialysis patients for each antibody response status was one for no responder (<50 AU/mL), nine for low responder (50–7,021 AU/mL), and 54 for high responder (≥7,021 AU/mL). The rate of high responders was 84% (54 of 64). Only uric acid was significantly different among these three categories (p = 0.01).

Discussion

In the present study, we found that the anti-SARS-CoV-2 spike antibody titer 4 weeks after the third dose of COVID-19 vaccine was comparable between hemodialysis patients and healthcare workers. We also found that the uric acid concentration, TSAT, and anti-SARS-CoV-2 spike antibody titer 1 week before the third dose of COVID-19 vaccine were correlated with the anti-SARS-CoV-2 spike antibody titer 4 weeks after the third dose of COVID-19 vaccine. In contrast, only the anti-SARS-CoV-2 spike antibody titer 1 week before the third dose of COVID-19 vaccine was correlated with the anti-SARS-CoV-2 spike antibody titer 12 weeks after the third dose of COVID-19 vaccine.

Several recent studies have reported the anti-SARS-CoV-2 spike antibody response against the third COVID-19 vaccination in hemodialysis patients [4,5]. One observational study involving 80 hemodialysis patients and 56 healthcare workers in Israel showed that the anti-SARS-CoV-2 spike antibody level after the third COVID-19 vaccination was lower in hemodialysis patients than in healthcare workers [4]. Another observational study involving 350 hemodialysis patients and 130 healthcare workers in Japan showed that the anti-SARS-CoV-2 spike antibody level after the third COVID-19 vaccination was comparable between hemodialysis patients and healthcare workers [5]. In the present study, the anti-SARS-CoV-2 spike antibody titer after the third COVID-19 vaccination was comparable between 64 Japanese hemodialysis patients and 18 healthcare workers. This inconsistency among study results might be explained by a difference in the ethnicity of patients because humoral immune responses to COVID-19 vaccination were reported to vary depending on ethnicity [9]. Further studies incorporating different ethnicities are necessary to assess the efficacy of the third COVID-19 vaccination in hemodialysis patients. These recent studies have also reported the anti-SARS-CoV-2 spike antibody response status after the third dose of COVID-19 vaccine in patients undergoing hemodialysis [4,5]. The first study reported that 88% of hemodialysis patients became high responders (>1,000 AU/mL) [4]. The second study reported that 87% of hemodialysis patients became high responders (≥7,021 AU/mL) [5]. In the present study, 84% of hemodialysis patients became high responders (≥7,021 AU/mL). These results suggest that the third dose of COVID-19 vaccine substantially improved the anti-SARS-CoV-2 spike antibody response in hemodialysis patients. It was shown that the anti-SARS-CoV-2 spike antibody level peaks 3 to 4 weeks after the third COVID-19 vaccination and then declines linearly with time [10]. In the present study, the anti-SARS-CoV-2 spike antibody titer decreased by approximately 50% between 4 weeks and 12 weeks after the third COVID-19 vaccination. Further research is necessary to determine the optimal timing of anti-SARS-CoV-2 spike antibody titer measurements in hemodialysis patients for subsequent COVID-19 vaccination.

Several studies reported that the anti-SARS-CoV-2 spike antibody level before the third COVID-19 vaccination was positively associated with the anti-SARS-CoV-2 spike antibody level in hemodialysis patients after the third COVID-19 vaccination [4,6,7]. In the present study, the anti-SARS-CoV-2 spike antibody titer 1 week before the third COVID-19 vaccination was positively correlated with that at 4 and 12 weeks after the third COVID-19 vaccination, which was consistent with the results of previous reports [4,6,7]. These results indicate that the degree of humoral immunity against SARS-CoV-2 before the third COVID-19 vaccination may influence the anti-SARS-CoV-2 spike antibody response in hemodialysis patients after the third COVID-19 vaccination.

Uric acid is a poor water-soluble molecule and for those with hyperuricemia, excess uric acid can precipitate as urate crystals in the blood and tissues [11]. Urate crystals stimulate granulocytes and monocytes through the assembly and activation of the NLRP3 inflammasome complex, thereby enhancing innate immunity [12]. However, the influence of uric acid on immune responses after vaccination remains unclear [13]. To the best of our knowledge, there are no reports on the relationship between serum uric acid concentration and antibody titer after vaccination. In our study, the serum uric acid concentration correlated negatively with the anti-SARS-CoV-2 spike antibody titer and antibody response status in hemodialysis patients after the third COVID-19 vaccination. Further research is necessary to investigate the relationship between serum uric acid concentration and anti-SARS-CoV-2 spike antibody titer in hemodialysis patients after the COVID-19 vaccination.

Ferritin and TSAT are widely and commonly used indicators of iron metabolism [14]. The serum ferritin concentration reflects the amount of iron stored in the body whereas TSAT indicates the availability of iron in the body. An observational study reported that a serum ferritin level greater than 600 ng/mL was associated with higher anti-SARS-CoV-2 spike antibody levels in hemodialysis patients [15]. Another observational study reported that a higher serum ferritin level was associated with lower anti-SARS-CoV-2 spike antibody levels in hemodialysis patients [16]. In the present study, no significant association was observed between the serum ferritin concentration and anti-SARS-CoV-2 spike antibody titer whereas TSAT was correlated negatively with the anti-SARS-CoV-2 spike antibody titer in hemodialysis patients after the third COVID-19 vaccination. Therefore, the relationship between iron metabolism and anti-SARS-CoV-2 spike antibody response is still controversial. Further research is necessary to elucidate the influence of iron metabolism on the anti-SARS-CoV-2 spike antibody response in hemodialysis patients after the COVID-19 vaccination.

This study has several advantages compared with previous studies [4–7]. First, we assessed the anti-SARS-CoV-2 spike antibody titers 1 week before and 4 and 12 weeks after the third COVID-19 vaccination. Second, we analyzed various clinical and demographic parameters associated with the anti-SARS-CoV-2 spike antibody titer after the third dose of COVID-19 vaccine in Asian individuals undergoing hemodialysis. The results of the present study might be useful for further studies to investigate the factors associated with the anti-SARS-CoV-2 spike antibody response to the third COVID-19 vaccination.

Several study limitations should be addressed. First, the patients were recruited from a single institution, which limits the external validity of the results. Second, the number of participants was low and this decreased the statistical power for detecting between-group differences. Third, patients with asymptomatic COVID-19 might have been included in this study although we excluded patients who developed COVID-19. Fourth, the anti-SARS-CoV-2 spike antibody titers were not compared between control and hemodialysis patient groups 12 weeks after the third COVID-19 vaccination, because we could not obtain the anti-SARS-CoV-2 spike antibody titer in healthcare workers 12 weeks after the third COVID-19 vaccination. Fifth, we did not assess clinical outcomes such as COVID-19 infection, hospitalization, and death, although there are several reports focusing on clinical outcomes as well as serology [17,18]. Therefore, large-scale multicenter studies incorporating an appropriate control group are necessary to validate the present study findings and the clinical effectiveness of COVID-19 vaccine in hemodialysis patients.

In conclusion, the anti-SARS-CoV-2 spike antibody titer after the third dose of COVID-19 vaccine was comparable between hemodialysis patients and healthcare workers. The uric acid concentration, TSAT, and anti-SARS-CoV-2 spike antibody titer before the third dose of COVID-19 vaccine were associated with the anti-SARS-CoV-2 spike antibody titer in hemodialysis patients after the third dose of COVID-19 vaccine.

Notes

Conflicts of interest

All authors have no conflicts of interest to declare.

Data sharing statement

The data presented in this study are available from the corresponding author upon reasonable request.

Authors’ contributions

Conceptualization, Methodology: KH, MS

Data curation, Formal analysis, Investigation: MS, TO

Writing–original draft: KH

Writing–review & editing: SO, YM

All authors read and approved the final manuscript.

Acknowledgments

We thank all medical staff members of the Mizue Yuai Clinic for their wonderful medical care and support. We thank J. Ludovic Croxford, PhD and Charles Allan, PhD, from Edanz for editing a draft of this manuscript.

Figure 1.

Study flow chart.

COVID-19, coronavirus disease 2019.

Figure 2.

Comparison of anti-SARS-CoV-2 spike antibody titers between hemodialysis patients (n = 64) and healthcare workers (n = 18).

Values are presented as the median (interquartile range). ^*p < 0.001, ^**p < 0.05.

NS, not significant; SARS-CoV-2, severe acute respiratory syndrome coronavirus 2.

Table 1.

Demographic and clinical characteristics

Characteristic	Hemodialysis patients	Healthcare workers	p-value
No. of subjects	64	18
Age (yr)	71.4 ± 11.7	45.9 ± 12.2	<0.001^*
Male sex	37 (57.8)	8 (44.4)	0.42
Body mass index (kg/m²)	21.9 ± 3.9	24.8 ± 5.8	0.02^*
Hemodialysis vintage (yr)	4.5 (2.0–9.0)	NA	NA
Dialysis frequency
Twice weekly	0 (0)	NA	NA
Thrice weekly	64 (100)	NA	NA
Dialysis type
Hemodialysis	23 (35.9)	NA	NA
Hemodiafiltration	41 (64.1)	NA	NA
Past or current smoking	12 (18.8)	7 (38.9)	0.11
Alcohol drinking	11 (17.2)	11 (61.1)	<0.001^*
Hypertension	39 (60.9)	3 (16.7)	0.001^*
Diabetes mellitus	28 (43.8)	1 (5.6)	0.002^*
Autoimmune disease	6 (9.4)	0 (0)	>0.99
Allergic disease	19 (29.7)	5 (27.8)	>0.99
Previous HBV infection	11 (17.2)	0 (0)	0.11
Previous HCV infection	2 (3.1)	0 (0)	>0.99
Previous syphilis infection	4 (6.3)	0 (0)	0.57
RAS inhibitor	24 (37.5)	2 (11.1)	0.04^*
Antihyperuricemic drug	14 (21.9)	4 (22.2)	>0.99
Statin	20 (31.3)	1 (5.6)	0.03^*
Erythropoiesis-stimulating agent	56 (87.5)	0 (0)	<0.001^*
HIF-PH inhibitor	4 (6.3)	0 (0)	0.57
Iron supplement	40 (63.5)	0 (0)	<0.001^*
Zinc supplement	7 (10.9)	0 (0)	0.34
Phosphate binder	51 (79.7)	0 (0)	<0.001^*
Vitamin D analog	54 (84.4)	0 (0)	<0.001^*
Calcimimetic	24 (37.5)	0 (0)	0.001^*
Corticosteroid	3 (4.7)	0 (0)	>0.99
Albumin (g/dL)	3.6 ± 0.5	NA	NA
White blood cell count (/μL)	7,136 ± 4,846	NA	NA
Lymphocyte count (/μL)	1147 ± 415	NA	NA
Hemoglobin (g/dL)	11.0 ± 1.2	NA	NA
Platelet count (×10⁴/μL)	21.2 ± 6.5	NA	NA
Blood urea nitrogen (mg/dL)	61.0 ± 15.9	NA	NA
Creatinine (mg/dL)	9.6 ± 2.8	NA	NA
Sodium (mEq/L)	138.8 ± 2.6	NA	NA
Potassium (mEq/L)	4.7 ± 0.7	NA	NA
Chloride (mEq/L)	101.8 ± 3.3	NA	NA
Total calcium (mg/dL)	8.3 ± 0.6	NA	NA
Phosphate (mg/dL)	5.2 ± 1.3	NA	NA
Magnesium (mg/dL)	2.5 ± 0.4	NA	NA
Uric acid (mg/dL)	6.9 ± 1.2	NA	NA
Total cholesterol (mg/dL)	160.0 ± 38.6	NA	NA
C-reactive protein (mg/dL)	0.11 (0.05–0.44)	NA	NA
iPTH (pg/mL)	178.6 ± 77.0	NA	NA
β2 microglobulin (mg/L)	28.4 ± 6.9	NA	NA
Ferritin (ng/mL)	183.5 (111.5–314.8)	NA	NA
Transferrin saturation (%)	30.0 ± 16.7	NA	NA
Zinc (μg/dL)	61.2 ± 13.4	NA	NA
Glycated hemoglobin (%)	5.8 ± 1.0	NA	NA
Glycoalbumin (%)	19.6 ± 4.3	NA	NA
nPCR (g/kg/day)	0.78 ± 0.23	NA	NA
Single-pool Kt/V	1.57 ± 0.43	NA	NA

Data are expressed as number only, mean ± standard deviation, number (%), or median (interquartile range).

HBV, hepatitis B virus; HCV, hepatitis C virus; HIF-PH, hypoxia-inducible factor prolyl hydroxylase; iPTH, intact parathyroid hormone; Kt/V, urea clearance; NA, not available; nPCR, normalized protein catabolic rate; RAS, renin-angiotensin system.

^*p < 0.05.

Table 2.

Simple and multiple linear regression analyses of the variables correlated with log–anti-SARS-CoV-2 spike antibody titer 4 weeks after the third BNT162b2 mRNA COVID-19 vaccination

Variable	Simple linear regression analysis		Multiple linear regression analysis^a
Variable	Standard coefficient	p-value	Standard coefficient	p-value
Body mass index	0.307	0.01^*	0.103	0.32
Diabetes mellitus	0.324	0.009^*	0.173	0.06
Blood urea nitrogen	–0.303	0.02^*	–0.083	0.44
Total calcium	0.301	0.02^*	0.171	0.07
Uric acid	–0.350	0.005^*	–0.203	0.02*
Total cholesterol	–0.227	0.07	–0.099	0.25
Transferrin saturation	–0.380	0.002^*	–0.269	0.003^*
nPCR	–0.301	0.02^*	–0.038	0.77
Log–anti-SARS-CoV-2 spike antibody titer 1 week before the third BNT162b2 mRNA COVID-19 vaccination	0.639	<0.001^*	0.440	<0.001^*

COVID-19, coronavirus disease 2019; log, logarithm; mRNA, messenger RNA; nPCR, normalized protein catabolic rate; SARS-CoV-2, severe acute respiratory syndrome coronavirus 2.

^aUsing variables with p < 0.10 in univariate analyses.

^*p < 0.05.

Table 3.

Simple and multiple linear regression analyses of the variables correlated with log–anti-SARS-CoV-2 spike antibody titer 12 weeks after the third BNT162b2 mRNA COVID-19 vaccination

Variable	Simple linear regression analysis		Multiple linear regression analysis^a
Variable	Standard coefficient	p-value	Standard coefficient	p-value
Diabetes mellitus	0.312	0.01^*	0.145	0.20
Blood urea nitrogen	–0.295	0.02^*	–0.043	0.73
Sodium	–0.234	0.06	–0.156	0.16
Total calcium	0.211	0.09	0.170	0.12
Uric acid	–0.332	0.007^*	–0.164	0.12
Total cholesterol	–0.249	0.048^*	–0.116	0.28
Transferrin saturation	–0.259	0.04^*	–0.167	0.12
nPCR	–0.267	0.04^*	–0.047	0.72
Log–anti-SARS-CoV-2 spike antibody titer 1 week before the third BNT162b2 mRNA COVID-19 vaccination	0.574	<0.001^*	0.410	<0.001^*

COVID-19, coronavirus disease 2019; log, logarithm; mRNA, messenger RNA; nPCR, normalized protein catabolic rate; SARS-CoV-2, severe acute respiratory syndrome coronavirus 2.

^aUsing variables with p < 0.10 in univariate analyses.

^*p < 0.05.

Table 4.

Patient characteristics categorized by the anti-SARS-CoV-2 spike antibody response status 4 weeks after the third BNT162b2 mRNA COVID-19 vaccination

Characteristic	No responder	Low responder	High responder	p-value
No. of subjects	1	9	54
Age (yr)	73.0	78.7 ± 12.1	70.1 ± 11.4	0.10
Male sex	1 (100)	4 (44.4)	32 (59.3)	0.70
Body mass index (kg/m²)	20.9	19.5 ± 2.5	22.3 ± 4.0	0.14
Hemodialysis vintage (yr)	26.0	3.0 (3.0–6.0)	4.5 (2.0–8.8)	0.22
Dialysis frequency				>0.99
Twice weekly	0 (0)	0 (0)	0 (0)
Thrice weekly	1 (100)	9 (100)	54 (100)
Dialysis type				>0.99
Hemodialysis	0 (0)	3 (33.3)	20 (37.0)
Hemodiafiltration	1 (100)	6 (66.7)	34 (63.0)
Past or current smoking	0 (0)	1 (11.1)	11 (20.4)	>0.99
Alcohol drinking	0 (0)	0 (0)	11 (20.4)	0.45
Hypertension	1 (100)	4 (44.4)	34 (63.0)	0.56
Diabetes mellitus	0 (0)	2 (22.2)	26 (48.1)	0.28
Autoimmune disease	0 (0)	2 (22.2)	4 (7.4)	0.28
Allergic disease	0 (0)	1 (11.1)	18 (33.3)	0.48
Previous HBV infection	0 (0)	2 (22.2)	9 (16.7)	0.71
Previous HCV infection	0 (0)	1 (11.1)	1 (1.9)	0.29
Previous syphilis infection	0 (0)	0 (0)	4 (7.4)	>0.99
RAS inhibitor	1 (100)	1 (11.1)	22 (40.7)	0.06
Antihyperuricemic drug	0 (0)	0 (0)	14 (25.9)	0.29
Statin	0 (0)	4 (44.4)	16 (29.6)	0.62
Erythropoiesis-stimulating agent	1 (100)	9 (100)	46 (85.2)	0.64
HIF-PH inhibitor	0 (0)	0 (0)	4 (7.4)	>0.99
Iron supplement	0 (0)	7 (77.8)	33 (62.3)	0.37
Zinc supplement	0 (0)	2 (22.2)	5 (9.3)	0.34
Phosphate binder	1 (100)	5 (55.6)	45 (83.3)	0.13
Vitamin D analog	0 (0)	9 (100)	45 (83.3)	0.08
Calcimimetic	0 (0)	4 (44.4)	20 (37.0)	0.83
Corticosteroid	0 (0)	1 (11.1)	2 (3.7)	0.40
Albumin (g/dL)	3.7	3.4 ± 0.3	3.6 ± 0.5	0.18
White blood cell count (/μL)	4,780	5,926 ± 2,045	7,386 ± 5,189	0.34
Lymphocyte count (/μL)	808	1,052 ± 325	1,169 ± 430	0.35
Hemoglobin (g/dL)	10.6	11.3 ± 1.2	10.9 ± 1.3	0.80
Platelet count (×10⁴/μL)	17.9	20.5 ± 5.7	21.4 ± 6.7	0.75
Blood urea nitrogen (mg/dL)	84.8	65.8 ± 12.4	59.8 ± 16.1	0.11
Creatinine (mg/dL)	12.3	9.0 ± 1.7	9.7 ± 2.9	0.35
Sodium (mEq/L)	141	139.7 ± 1.3	138.6 ± 2.7	0.30
Potassium (mEq/L)	4.8	4.8 ± 0.5	4.7 ± 0.8	0.99
Chloride (mEq/L)	103	103.2 ± 2.2	101.6 ± 3.4	0.29
Total calcium (mg/dL)	6.5	8.1 ± 0.5	8.4 ± 0.6	0.10
Phosphate (mg/dL)	5.0	5.4 ± 1.6	5.2 ± 1.3	0.86
Magnesium (mg/dL)	2.4	2.5 ± 0.3	2.5 ± 0.4	0.96
Uric acid (mg/dL)	8.3	7.7 ± 0.7	6.7 ± 1.2	0.01^*
Total cholesterol (mg/dL)	180	176.9 ± 35.4	156.9 ± 39.0	0.25
C-reactive protein (mg/dL)	0.05	0.14 (0.12–0.49)	0.10 (0.05–0.43)	0.20
iPTH (pg/mL)	17	198.2 ± 58.1	178.3 ± 77.3	0.14
β2 microglobulin (mg/L)	34.0	26.1 ± 6.6	28.7 ± 6.9	0.40
Ferritin (ng/mL)	528.7	193.0 (112.2–261.0)	179.6 (110.4–307.8)	0.36
Transferrin saturation (%)	91.1	30.4 ± 10.6	28.8 ± 15.5	0.18
Zinc (μg/dL)	64	59.0 ± 13.3	61.5 ± 13.6	0.81
Glycated hemoglobin (%)	4.0	5.2 ± 0.5	5.8 ± 1.0	0.07
Glycoalbumin (%)	16.3	16.3 ± 3.7	19.5 ± 4.4	0.11
nPCR (g/kg/day)	0.95	0.89 ± 0.23	0.76 ± 0.22	0.26
Single-pool Kt/V	1.50	1.60 ± 0.22	1.56 ± 0.46	0.75

Data are expressed as number only, mean ± standard deviation, number (%), or median (interquartile range).

The anti-SARS-CoV-2 spike antibody response status was defined as follows: no responder (anti-SARS-CoV-2 spike antibody titer < 50 AU/mL), low responder (50–7,021 AU/mL), and high responder (≥7,021 AU/mL).

COVID-19, coronavirus disease 2019; HBV, hepatitis B virus; HCV, hepatitis C virus; HIF-PH, hypoxia-inducible factor prolyl hydroxylase; iPTH, intact parathyroid hormone; Kt/V, urea clearance; mRNA, messenger RNA; nPCR, normalized protein catabolic rate; RAS, renin-angiotensin system; SARS-CoV-2, severe acute respiratory syndrome coronavirus 2.

^*p < 0.05.

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