key: cord-0949515-3pm40z3s
authors: Broseta, José Jesús; Rodríguez-Espinosa, Diana; Rodríguez, Néstor; Mosquera, María del Mar; Marcos, María Ángeles; Egri, Natalia; Pascal, Mariona; Soruco, Erica; Bedini, José Luis; Bayés, Beatriu; Maduell, Francisco
title: Humoral and Cellular Responses to mRNA-1273 and BNT162b2 SARS-CoV-2 Vaccines Administered to Hemodialysis Patients
date: 2021-06-24
journal: Am J Kidney Dis
DOI: 10.1053/j.ajkd.2021.06.002
sha: e20022416e11a7006060d0b9d86f1472d1680e77
doc_id: 949515
cord_uid: 3pm40z3s

RATIONALE AND OBJECTIVE: Patients with kidney failure requiring maintenance dialysis have a higher risk of infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and worse clinical outcomes after coronavirus disease 2019 (COVID-19) than the general population. Therefore, immunization against SARS-CoV-2 with effective vaccines is an important component of health-maintenance strategies for these patients. This study evaluated the humoral and cellular responses to messenger RNA (mRNA) SARS-CoV-2 vaccines in this population. STUDY DESIGN: Observational prospective, multi-center cohort study. SETTING AND PARTICIPANTS: Two hundred five patients treated at three dialysis units at the Hospital Clínic of Barcelona (Spain) were vaccinated from February 3 to April 4, 2021 and followed until April 23, 2021. EXPOSURE: Immunization with either the mRNA-1273 (Moderna) or BNT162b2 (Pfizer-BioNTech) SARS-CoV-2 mRNA vaccine. OUTCOMES: Seroconversion, defined as the detection of IgG antibodies to the receptor-binding domain of the S1 spike antigen of SARS-CoV-2 (anti–S1-RBD IgG), and the identification of activated CD4(+) T cells 3 weeks after completing vaccination. Anti-S1-RBD IgG levels were also analyzed as a secondary outcome. ANALYTICAL APPROACH: Univariate and multivariable logistic and multiple linear regression models were used to evaluate the associations between vaccination and study outcomes. RESULTS: 97.7% of 175 vaccinated patients who were seronegative at baseline developed a response (humoral, cellular, or both). 95.4% of these patients seroconverted, while 62% of those tested for a cellular immunity had a positive response. Greater age and immunosuppressive treatment were associated with lower antibody levels. LIMITATIONS: Mandatory vaccine administration by health authorities. Anti-S1-RBD IgG levels were reported up to 150 U/mL and cellular immune responses were characterized qualitatively. Antibody assay and cellular response assessment may not be comparable with previously published laboratory approaches. CONCLUSIONS: Immunization with mRNA vaccines generated a humoral and cellular immune response in a high proportion of patients with kidney failure receiving maintenance dialysis. These findings as well as the high risk of infection and poor clinical outcomes among these patients make their vaccination a health priority.

During the past year, numerous coronavirus disease 2019 (COVID- 19) outbreaks have occurred in hemodialysis units because of their patients' high risk for viral exposure, given that they share transport and dressing rooms and they spend, on average, 12 hours a week with their peers and healthcare professionals 1, 2, 3 . Moreover, once infected, patients with kidney failure receiving hemodialysis have poor clinical outcomes. They have more hospital admissions, more extended hospital stays, and greater mortality than the general population 4, 5 . In fact, during the disease's first wave in 2020, we found a mortality rate of 34% among hemodialysis patients from our three affiliated units 6 , strikingly higher than the overall 9.7% seen in all admitted patients in our hospital 7 . These poor outcomes have been attributed to the multiple comorbidities afflicting these patients as well as their increased age, fragility, and immunologically deficient state 6, 8 . Considering the combination of these high-risk factors, this population must be promptly immunized against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) as recommended by several nephrology societies 9-12 .

There are currently several vaccines available and approved for use in the general population.

However, despite the shortage of data on their effectiveness, some authors have suggested using the mRNA vaccines for special populations such as patients with kidney failure receiving hemodialysis 13 . Two mRNA vaccines have been approved for use: mRNA-1273 (Moderna) and the BNT162b2 (Pfizer-BioNTech). Both consist of a lipid-encapsulated nanoparticles that encapsulate mRNA encoding the prefusion-stabilized full-length SARS-CoV-2 spike, which induces T-helper, cytotoxic Tcell, and humoral immune responses 14 . Randomized trials showed 94.1% and 95% efficacy at preventing COVID-19, with complete absence of hospital admissions and deaths among those vaccinated 15, 16 . Routine data have suggested these vaccines prevent 94% of symptomatic COVID-19 cases, 85-87% of hospital admissions, and 92% of severe disease 17,18 . J o u r n a l P r e -p r o o f Even though the most appropriate method to evaluate a vaccine response is by assessing clinical outcomes (e.g., hospital admissions and mortality), there is an urgent demand to immunize kidney failure patients receiving hemodialysis. Furthermore, the immunodeficient state of this population, as demonstrated by their reduced seroconversion in other immunization programs such as that against hepatitis B virus 19 , has generated great concern about the effectiveness of SARS-CoV-2 vaccines to elicit real-life protection from severe COVID-19. Consequently, despite the CDC not recommending antibody testing post-vaccination to assess individuals' response to immunization (nor are there FDA-authorized tests for this purpose due to the heterogeneity of test results and scarce external validation), many studies have evaluated vaccine response based on capacity to generate an adaptive immune response, whether it be humoral (i.e., the formation of antibodies that prevent viral entry into cells) or cellular (i.e., the activation of specific T cells that kill infected cells and thus prevent viral replication). A recent report by Irsara et al. found a good correlation between level of IgG antibodies to the receptor-binding domain of the S1 spike antigen of SARS-CoV-2 (anti-S1-RBD IgG) measured by the Siemens SARS-CoV-2 IgG (sCOVG) assay and viral neutralization levels, suggesting their potential use as a surrogate for virus neutralization capacity 20 . Therefore, even though rapidly emerging results on both mRNA vaccines' efficacy in the hemodialysis population 21,22 must be interpreted carefully, there is hope that these cellular and humoral responses can act as indirect signs of COVID-19 protection.

Currently, the literature is lacking in large cohorts that include both the mRNA-1273 and BNT162b2 vaccine in similar proportions. This study aims to assess the humoral and cellular responses to both SARS-CoV-2 mRNA vaccines in maintenance hemodialysis patients while looking for potential predictors of antibody generation and intensity.

This observational, prospective, multi-center study to evaluate immunogenicity in terms of antibody response and T-cell activation after SARS-CoV-2 mRNA vaccination in hemodialysis patients was 

All prevalent maintenance hemodialysis patients over 18 years old in the three dialysis facilities were considered for inclusion. Patients were excluded if they were previously vaccinated in other healthcare centers, refused vaccination, were admitted to the hospital during the inclusion period, had a history of SARS-CoV-2 infection less than three months before the vaccination period finalized, or declined to participate. Participants were classified according to the cellular and humoral responses observed after completing vaccination. Seropositive patients (those who were positive for anti-S1-RBD IgG at baseline) were excluded from the humoral response analysis. Cellular response was only available in a subset of the study participants, as there were logistic impediments that required laboratory samples to be received during the morning.

Humoral response was measured in all patients at three different timepoints (baseline, immediately before administering the second dose, and three weeks thereafter) with the Siemens Healthineers Atellica® IM SARS-CoV-2 IgG (sCOVG) assay, which detects IgG antibodies to the receptor-binding domain of the S1 spike antigen of SARS-CoV-2 (anti-S1-RBD IgG). The sample is considered non-reactive when the result is less than 1 or reactive when greater than or equal to 1, with a maximum measurable level of up to 150 U/mL. According to the manufacturer, this test has 96.41% (95% CI, 92.74-98.54%) sensitivity and 99.9% (95% CI, 99.63-99.99%) specificity.

Heparinized peripheral blood was collected from study participants to measure CD4 + T cell response at three weeks after completing vaccination by an intracellular cytokine stimulation assay.

For detection of cells expressing CD69 and intracellular interferon γ (IFN-γ), white blood cells (WBCs) from each study participant were stimulated with spike and nucleocapsid SARS-CoV-2 peptide pools (Miltenyi Biotec), with a negative (vehicle) and a positive (staphylococcal enterotoxin B superantigen) control. Flow cytometric detection of more than ten events of CD4 + IFN-γ + CD69 + , with greater than 2-fold change compared with the unstimulated condition, was considered a positive peptide-specific response. All assays were performed at 37ºC, 5% CO 2 , and 95% humidity. Flow SARS-CoV-2 infection, the use of immunosuppressive therapy, and the most recent available albumin, C-reactive protein (CRP), and white and red blood cell counts. These data were collected at baseline from electronic medical records and were considered as potential confounding variables for vaccine response in these analyses.

The primary outcomes evaluated in this study were the qualitative humoral and cellular responses to the mRNA vaccine. Secondary evaluated outcomes were quantitative anti-S1-RBD IgG levels among the patients who were seronegative at baseline. A comparison between them and the remaining patients who were seropositive was also performed.

Quantitative variables are reported with mean and standard deviation, while presence or absence of response is reported with absolute and relative frequencies. Univariate analysis was used to estimate the associations between vaccination and outcomes. Differences in demographic and clinical variables (sex, race, type of dialysis unit, diabetes, immunosuppressive therapy) and humoral and cellular responses between responder and non-responder groups were analyzed with the χ 2 test or Fisher's exact test when one or more expected values were less than five or the data were very unequally distributed among the table's cells. The normal distribution of the quantitative variables was tested with the Shapiro-Wilk test and Q-Q plots. Comparison of quantitative variables between two groups were made with the U-Mann Whitney test when non-normal (age, dialysis vintage, Kt/V, BMI, CRP, white blood cells, lymphocytes, and albumin) or the independent Student's t-test when normally distributed (hemoglobin). The comparison of anti-S1-RBD IgG levels between groups was made by the independent-samples median test as we performed a semi-quantitative test with a maximum J o u r n a l P r e -p r o o f detection limit of 150 U/mL. For analyses involving more than two groups, the Kruskal-Wallis H test or analysis of variance (ANOVA) were performed if variables were non-normal or normally distributed, respectively. A two-sided p-value inferior to 0.05 was considered statistically significant.

Variables that were associated with the chosen outcome (p < 0.05) were also entered into the multivariable logistic and multiple linear regression models. Odds ratio, mean or median differences, or exponentiated ß-coefficient are presented as effect measures of each studied variable, accordingly.

Analyses were performed with IBM SPSS® Statistics 26th version and the graphics with GraphPad Prism® 8th version.

All patients gave their written informed consent to participate in this study, which was approved by the institute's committee on human research. The study was conducted following the World Medical Association Declaration of Helsinki, national and local laws, and good clinical practice standards.

Two hundred and five patients were included in the study. Humoral response was assessed in 175 patients who received both doses, while cellular response was measured in 69 (39.4%). The number of seropositive individuals at baseline, the vaccine received, and reasons for loss to follow-up at each stage of the study are described in Figure 1 . Patients' demographics and clinical characteristics, both overall and grouped by mRNA vaccine received, are detailed in Table 1 . Table 2) . This model was statistically significant by the Hosmer and Lemeshow test (χ2 = 15.9, p = 0.04), explained 56.7% (Nagelkerke R 2 ) and correctly classified 98.8% of cases.

Anti-S1-RBD IgG levels generated are shown in Figure 3A . Lower levels of anti-S1-RBD IgG were correlated with higher age (p < 0.001) ( Figure 3B ), type of dialysis unit (p = 0.02), diabetes (p=0.04), immunosuppressive therapy (p < 0.01), lower albumin level (p = 0.04, and lower lymphocyte count (p = 0.04). In the multiple linear regression model, age (ß = -0.25, p = 0.001), type of dialysis unit (ß = 0.2, p = 0.01), and immunosuppressive treatment (ß = -3.6, p < 0.001) maintained statistical significance. This model was statistically significant (p < 0.001) but had a low predictive capacity of 17.1% (adjusted R 2 ) of the cases.

Eight of these 175 patients did not generate anti-S1-RBD IgG antibodies ( Table 3) . Four of these eight non-responders were on immunosuppressive therapy (three patients were treated with tacrolimus, of whom two were liver transplant recipients; one had a failed kidney graft who continued J o u r n a l P r e -p r o o f to take immunosuppressors to avoid HLA sensitization; and one was treated with eculizumab as a treatment for atypical hemolytic uremic syndrome). Of the remaining four, three were elderly, and one had no other apparent risk factor besides having type 2 diabetes.

Regardless of vaccine received, every patient who was seropositive at baseline developed antibody levels that were significantly higher than those who were seronegative at baseline (p <0.001), with all but one reaching levels over 150 UI/mL ( Figure 3C ). These baseline-seropositive patients also had a higher response with one vaccine dose than did baseline-seronegative patients after two doses (133.95 ± 37.4 vs. 86.2 ± 59.83 U/mL, p < 0.001).

T-cells specifically activated by either SARS-CoV-2 nucleocapsid and spike proteins were detected in 46 of the 69 (62%) evaluated patients. Type of dialysis unit significantly correlated with a positive cellular response (p = 0.03). No other associations were found between any of the analyzed potential response predictors (Table 4) ; thus, multivariable analysis was not performed. Twenty-three patients mounted a humoral but not a cellular response, while four did the opposite (Table 3 ). There was no statistically significant correlation between both immune responses (p = 0.8) or between positive cellular response and higher levels of anti-S1-RBD IgG (p = 0.3).

Three patients who received both vaccine doses became infected with SARS-CoV-2. One developed severe COVID-19 that required hospital admission. He received the BNT162b2 vaccine and did not mount a humoral response after the first dose (data regarding cellular or humoral responses following the second dose were not available due to loss to follow-up). The other two patients had asymptomatic SARS-CoV-2 infections that were detected by a monthly nasopharyngeal reverse transcriptase-polymerase chain reaction screening program. Both had developed a humoral response J o u r n a l P r e -p r o o f after the first mRNA-1273 vaccine dose (anti-S1-RBD IgG levels of 2.25 and 14.16 U/mL, respectively) and both had anti-S1-RBD IgG levels > 150 U/mL after the second dose.

The key outcomes that the nephrology community and patients are seeking to improve with SARS-CoV-2 immunization programs are COVID-19 mortality and ICU and hospital admissions.

Whether mRNA vaccines can significantly improve these 'hard' outcomes in patients with kidney failure receiving hemodialysis is yet to be determined. However, given concern regarding the vaccine's efficacy in this population, and until the aforementioned clinical outcomes are studied, one available approach is to evaluate how these vaccines elicit immunity to SARS-CoV-2 by examining T-cell activation, seroconversion, and anti-S1-RBD IgG levels 14 .

Under this premise, our multi-center cohort immunization program study of 205 hemodialysis patients with mRNA vaccines was successful. Of the 175 seronegative patients at baseline who received both vaccine doses, 97.7% developed a response (humoral, cellular, or both) and 95.4% seroconverted. By contrast, only 62% of those tested developed cellular immunity.

Currently, there are scarce data on the cellular response to commercially available mRNA vaccines among maintenance hemodialysis patients. There is only one general population report where half of the baseline seronegative patients generated T-cell responses after a single dose of the BNT162b2 vaccine 23 . The only available data after complete vaccination comes from three studies. In comparison to them, our results show percentages of T-cell activation that are closer to the general population (88.2%) 24 than to those in kidney transplant recipients (5.13%-35%) 25, 26 . Even so, this is an inadequate response, which is consistent with the response reported after hepatitis B virus vaccination of maintenance hemodialysis patients 27 . No correlations were found between cellular and humoral J o u r n a l P r e -p r o o f responses, nor with other studied predictors like age or immunosuppressive therapy, except for the type of dialysis, keeping with other published reports 23 .

Regarding the humoral response, we found that 95.4% generated anti-S1-RBD IgG in response to either mRNA-1273 or BNT162b2, resembling results reported in the vaccine clinical trials 28, 29 .

Emerging data on the humoral response of other hemodialysis cohorts have shown similar seroconversion results ranging from 82 to 96%. All but the Frantzen et al study (244 patients) 30 had a smaller number of participants than ours 21, 22, [31] [32] [33] [34] . Moreover, to our knowledge ours is the largest hemodialysis cohort to have evaluated the immune response to the mRNA-1273 vaccine 22 . The strongest predictors of humoral vaccine response and antibody levels seen in our results are concordant with those reported across other publications such as age, immunosuppressive treatment, and previous SARS-CoV-2 infection 22, 35, 36 . A correlation between seroconversion, its intensity, and patient age was seen in our findings, as also observed in other previously reported results on SARS-CoV-2 mRNA vaccines 28, 31, 37 . This was expected, given that age has been previously associated with an impaired ability to mount a robust immune humoral or cellular response 38 . However, when comparing agematched patients receiving maintenance hemodialysis with the general population, what stands out is that the former have a slower pace of seroconversion 31 . This may be related to the widely-described impaired immune response of maintenance hemodialysis patients found in other immunization programs 19, 27, 39 , though it seems not to be relevant when evaluating seroconversion after completing the vaccination scheme in the peritoneal dialysis population 40 . Patients will continue to be monitored for the presence of anti-S1-RBD IgG in serum in subsequent months, given that the duration of the vaccine response in patients with CKD-related immune deficiency is unknown and that they may serorevert faster than the general population.

In accordance with the data observed in studies that evaluate the vaccine response in kidney transplant recipients 25, [41] [42] [43] [44] , we found that the use of immunosuppressive therapy is a predictor of weak response in comparison to non-immunosuppressed participants, with fewer seroconverted patients and significantly lower anti-S1-RBD IgG levels in those who do generate a humoral response. Eleven participants in our study were on immunosuppressive treatment: 4 did not develop a humoral response to the complete vaccination, and five did respond but mounted low anti-S1-RBD IgG levels. In addition, every patient on corticosteroid treatment seroconverted, while none on tacrolimus did. This weakened anti-S1-RBD IgG production could be secondary to the tacrolimus inhibition of T-helper cell differentiation, resulting in a reduced B-cell activation 45 . For these reasons, some authors have proposed that the administration of a third dose may be beneficial in patients taking immunosuppressive medication 41 .

Our results confirm that seropositive patients at baseline produce a more intense humoral response 23, 31, 46 , reaching anti-S1-RBD IgG levels with the first dose as high as seronegative patients achieve after the second dose. However, findings regarding antibody levels must be interpreted carefully: even though there is evidence of a correlation between anti-S1-RBD IgG levels and viral neutralization 20 , their amount cannot be reliably correlated with higher protection because real-world information on prevention of severe COVID-19 after vaccination in hemodialysis patients is lacking.

In this regard, the two patients from our cohort infected with SARS-CoV-2 after completing vaccination remained asymptomatic throughout the duration of the infection. Important limitations of our study include that our microbiology laboratory was only able to report anti-S1-RBD IgG levels up to 150 U/mL and to provide a qualitative assessment of cellular response, limiting the complete analysis of the immune response's intensity. Moreover, we found substantial heterogeneity of antibody measurement assays, making it difficult to compare the antibody J o u r n a l P r e -p r o o f levels and cellular responses measured in our study. These two points hamper the generalizability of our results.

In conclusion, even though real-life clinical protection from COVID-19 in this population is yet to be seen, we found that immunization programs were effective in generating an overall immune response in patients with kidney failure receiving hemodialysis. These findings, together with the high risk of infection and poorer outcomes among these patients, makes their vaccination a health priority, with special attention to patients on immunosuppressive treatment and of older age. Further studies are needed to evaluate the maintenance of these immune responses and the potential need for booster doses. J o u r n a l P r e -p r o o f 

COVID-19 Outbreak in an Urban Hemodialysis Unit

COVID-19 Outbreak in a Large Hemodialysis Center

Infection in Hemodialysis Patients Detected Using Serologic Screening

Clinical Characteristics of and Medical Interventions for COVID-19 in Hemodialysis Patients in Wuhan

Presentation and Outcomes of Patients with ESKD and COVID-19

SARS-CoV-2 infection in a spanish cohort of CKD-5D patients: Prevalence, clinical presentation, outcomes, and de-isolation results

COVID-19 vaccines: modes of immune activation and future challenges

Efficacy and Safety of the mRNA-1273 SARS-CoV-2 Vaccine

Safety and Efficacy of the BNT162b2 mRNA Covid-19 Vaccine

BNT162b2 mRNA Covid-19 Vaccine in a Nationwide Mass Vaccination Setting

Covid-19: First doses of vaccines in Scotland led to a substantial fall in hospital admissions

Factors affecting effectiveness of vaccination against hepatitis B virus in hemodialysis patients

Humoral Response to the Pfizer BNT162b2 Vaccine in Patients Undergoing Maintenance Hemodialysis

Antibody Response to mRNA-1273

SARS-CoV-2 Vaccine in Hemodialysis Patients with and without Prior COVID-19

Effect of previous SARS-CoV-2 infection on humoral and T-cell responses to single-dose BNT162b2 vaccine. The Lancet

COVID-19 vaccine BNT162b1 elicits human antibody and TH1 T cell responses

Cellular and humoral response after mRNA-1273 SARS-CoV-2 vaccine in kidney transplant recipients

Impaired humoral and cellular immunity after SARS-CoV2 BNT162b2 (Tozinameran) prime-boost vaccination in kidney

Safety and Immunogenicity of Two RNA-Based Covid-19 Vaccine Candidates

An mRNA Vaccine against SARS-CoV-2 -Preliminary Report

Efficacy of the BNT162b2 mRNA Covid-19 Vaccine in a hemodialysis cohort. Nephrology, dialysis, transplantation : official publication of the European Dialysis and Transplant Association -European Renal Association

Antibody response to BNT162b2 vaccine in maintenance hemodialysis patients

Antibody response to mRNA SARS-CoV-2 vaccine among dialysis patients -a prospectivecohort study

Seroprevalence of antibody to S1 spike protein following vaccination against COVID-19 in patients receiving hemodialysis: a call to arms

Experience with SARS-COV-2 BNT162b2 mRNA vaccine in dialysis patients

Early Humoral Responses of Hemodialysis Patients after COVID-19 Vaccination with BNT162b2

Humoral response to SARS-CoV-2-vaccination with BNT162b2 (pfizer-biontech) in patients on hemodialysis

Safety and Immunogenicity of SARS-CoV-2 mRNA-1273 Vaccine in Older Adults

Aging of the immune system: Mechanisms and therapeutic targets

Influenza A/H1N1 vaccine in patients treated by kidney transplant or dialysis: A cohort study

Humoral response of mRNA-1273 SARS-CoV-2 vaccine in peritoneal dialysis patients. transplantation : official journal of the American Society of Transplantation and the American Society of Transplant Surgeons

Post-vaccine anti-SARS-CoV-2 spike protein antibody development in kidney transplants recipients

American journal of transplantation : official journal of the American Society of Transplantation and the American Society of Transplant Surgeons

Inhibition of T Helper Cell Differentiation by Tacrolimus or Sirolimus Results in Reduced B-Cell Activation: Effects on T Follicular Helper Cells

Correspondence Antibody response to first BNT162b2 dose in previously SARS-CoV-2-infected individuals. The Lancet

Acknowledgments: We would like to publicly recognize the nursing staff and administrative assistant of the Department of Dialysis for their help and support in this study's execution.