Seroresponse to SARS-CoV-2 Vaccines Among Maintenance Dialysis Patients.

To the Editor:

As of October 2021, 3 SARS-CoV-2 vaccines are available in the United States, and all appear highly effective in the general population. Studies suggest high seroresponse to messenger RNA vaccines among maintenance dialysis patients, albeit lower than that in the general population.1, 2, 3, 4, 5, 6 Data regarding adenoviral vector vaccines and predictors of vaccine nonresponse are limited by small sample sizes. Accordingly, we retrospectively analyzed seroresponse to SARS-CoV-2 vaccines among maintenance dialysis patients, updating an earlier report.

DCI is a national not-for-profit provider caring for more than 15,000 patients at 260 outpatient dialysis clinics across 29 states. As of January 2021, DCI physicians had the option of activating a SARS-CoV-2 vaccine protocol, in which anti–spike immunoglobulin G antibodies (SAb-IgG) were measured monthly with routine lab work (details in Item S1). We obtained demographic and clinical data, vaccination dates, and SAb-IgG titers from the DCI electronic health record. We excluded patients with previously diagnosed COVID-19 or positive SAb-IgG titer before or within 10 days after first vaccine dose.

In primary analyses, seroresponse was defined by at least one ≥1 SAb-IgG titer ≥1 U/L at 14-74 days after completion of a vaccine series. Because samples for antibody titers were drawn alongside monthly labs, most patients have 2 assessments in this 60-day period. Associations of demographic and clinical factors with vaccine seroresponse were analyzed using multivariable log Poisson regression with robust variances. Secondary analyses used alternate definitions of vaccine seroresponse: (1) ≥1 SAb-IgG titer ≥2 U/L at 14-74 days after vaccine series completion, and (2) SAb-IgG titer ≥1 U/L on the first assessment at least 14 days after vaccine series completion. This study was reviewed and approved by the WCG IRB (Work Order 1-1456342-1) with exemption for informed consent. Statistical analyses were performed using SAS v9.4.

Between January 1 and June 30, 2021, 1,528 patients (437 BNT162b2/Pfizer, 766 mRNA-1273/Moderna, and 325 Ad26.COV2.S/Janssen recipients) across 130 dialysis facilities had SAb-IgG titers measured after SARS-CoV-2 vaccination (Fig S1). Baseline characteristics were similar to those of the broader DCI vaccinated patient population. Between 14 and 74 days after vaccine series completion, 437 (29%), 946 (62%), and 145 (9%) had 1, 2, and more than 2 titers checked, respectively. BNT162b2/Pfizer recipients tended to be older (Table 1 ).

Table 1

Patient Characteristics by SARS-CoV-2 Vaccine Administered

Demographics	All Vaccinated DCI Patientsa (N = 9,599)	Study Patients
		Overall (N = 1,528)	BNT162b2/Pfizer (n = 437 [29%])	mRNA-1273/Moderna (n = 766 [50%])	Ad26.COV2.S/Janssen (n = 325 [21%])	Pe
Age, y	64.9 ± 13.5	64.2 ± 13.5	66.8 ± 12.9	64.0 ± 13.9	61.3 ± 12.6	<0.001
Female sex	3,901 (40.6%)	646 (42.3%)	191 (43.7%)	308 (40.2%)	147 (45.2%)	0.2
Race						<0.001
White	4,639 (48.3%)	768 (50.3%)	198 (45.3%)	447 (58.4%)	123 (37.8%)
Black	3,287 (34.2%)	356 (23.3%)	80 (18.3%)	116 (15.1%)	160 (49.2%)
Native American	262 (2.7%)	126 (8.3%)	61 (14.0%)	60 (7.8%)	5 (1.5%)
Asian/Pacific Islander	347 (3.6%)	93 (6.1%)	49 (11.2%)	37 (4.8%)	7 (2.2%)
Other/unknown	1,064 (11.1%)	185 (12.1%)	49 (11.2%)	106 (13.8%)	30 (9.2%)
Hispanic ethnicity	590 (6.2%)	205 (13.4%)	63 (14.4%)	134 (17.5%)	8 (2.5%)	<0.001
Dialysis vintage, mo	48.9 ± 56.1	53.0 ± 58.1	50.9 ± 57.6	52.4 ± 57.0	57.4 ± 61.2	0.3
Body mass index, kg/m2	28.8 ± 7.3	28.4 ± 7.1	28.4 ± 7.4	28.1 ± 6.4	29.2 ± 8.0	0.06
Long-term care facility	1,046 (10.9%)	139 (9.1%)	41 (9.4%)	69 (9.0%)	29 (8.9%)	0.9
Home dialysis	1,335 (13.9%)	224 (14.7%)	59 (13.5%)	130 (17.0%)	35 (10.8%)	0.02
Peritoneal dialysis	1,225 (12.8%)	198 (13.0%)	50 (11.4%)	113 (14.8%)	35 (10.8%)
Home hemodialysis	110 (1.2%)	26 (1.7%)	9 (2.1%)	17 (2.2%)	0 (0.0%)
Adequate dialysis doseb	7,155 (74.5%)	1,205 (78.9%)	350 (80.1%)	597 (77.9%)	258 (79.4%)	0.7
Serum albumin, g/dL	3.8 ± 0.4	3.9 ± 0.4	3.9 ± 0.4	3.9 ± 0.4	3.8 ± 0.4	0.05
Other vaccines within 14 days	881 (9.2%)	129 (8.4%)	40 (9.2%)	62 (8.1%)	27 (8.3%)	0.8
Pneumococcal	186 (1.9%)	32 (2.1%)	5 (1.1%)	21 (2.7%)	6 (1.9%)	0.2
HBV	717 (7.5%)	101 (6.6%)	35 (8.0%)	44 (5.7%)	22 (6.8%)	0.3
Influenza	38 (0.4%)	6 (0.4%)	2 (0.5%)	4 (0.5%)	0 (0.0%)	0.9
HBV seroimmunityc	6,231 (64.9%)	1,099 (71.9%)	317 (72.5%)	557 (72.7%)	225 (69.2%)	0.3
Potential immunosuppression	1,738 (18.1%)	276 (18.1%)	94 (21.5%)	126 (16.5%)	56 (17.2%)	0.08
Immune-modulating medicationsd	1,260 (13.1%)	197 (12.9%)	69 (15.8%)	91 (11.9%)	37 (11.4%)	0.1
Prior transplant	670 (7.0%)	102 (6.7%)	32 (7.3%)	53 (6.9%)	17 (5.2%)	0.5
Immunodeficiency disorder	342 (3.6%)	71 (4.7%)	23 (5.3%)	31 (4.1%)	17 (5.2%)	0.5
Hospitalization within 14 days	1,195 (12.5%)	194 (12.7%)	58 (13.3%)	103 (13.5%)	33 (10.2%)	0.3
Disability	430 (4.5%)	62 (4.1%)	16 (3.7%)	30 (3.9%)	16 (4.9%)	0.7
Tobacco use	1,530 (15.9%)	205 (13.4%)	48 (11.0%)	101 (13.2%)	56 (17.2%)	0.04
Alcohol abuse disorder	1,023 (10.7%)	143 (9.4%)	38 (8.7%)	71 (9.3%)	34 (10.5%)	0.7
Drug abuse disorder	441 (4.6%)	51 (3.3%)	14 (3.2%)	27 (3.5%)	10 (3.1%)	0.9
No. of comorbidities	3.0 ± 1.8	2.9 ± 1.7	2.9 ± 1.6	2.9 ± 1.6	3.1 ± 1.8	0.1
Diabetes mellitus	5,765 (60.1%)	909 (59.5%)	269 (61.6%)	437 (57.1%)	203 (62.5%)	0.2
Hypertension	8,023 (83.6%)	1,310 (85.7%)	371 (84.9%)	657 (85.8%)	282 (86.8%)	0.8
Congestive heart failure	2,090 (21.8%)	298 (19.5%)	72 (16.5%)	150 (19.6%)	76 (23.4%)	0.06
COPD	1,500 (15.6%)	230 (15.1%)	65 (14.9%)	100 (13.1%)	65 (20.0%)	0.01
Stroke/cerebrovascular disorder	909 (9.5%)	114 (7.5%)	33 (7.6%)	51 (6.7%)	30 (9.2%)	0.3
Peripheral vascular disease	1,297 (13.5%)	178 (11.7%)	43 (9.8%)	78 (10.2%)	57 (17.5%)	0.001
Thyroid disorder	1,558 (16.2%)	248 (16.2%)	64 (14.7%)	136 (17.8%)	48 (14.8%)	0.3
History of cancer	1,018 (10.6%)	136 (8.9%)	41 (9.4%)	74 (9.7%)	21 (6.5%)	0.2

Continuous variables given as mean ± standard deviation. Abbreviations: COPD, chronic obstructive pulmonary disease; SARS-CoV-2, severe acute respiratory syndrome coronavirus 2; DCI, Dialysis Clinic, Inc.

Patients fully vaccinated with an emergency-use approved vaccine series of one type without additional doses as of June 30, 2021, excluding those with prior COVID-19.

Hemodialysis single-pool Kt/V≥1.2 or peritoneal dialysis weekly Kt/V≥1.7.

Hepatitis B virus (HBV) seroimmunity defined as antibody to HBV surface antigen ≥10 mIU/mL.

Medications include anti-inflammatory medications, antineoplastic agents, corticosteroids, and certain anti-infective medications.

P value for comparisons across the 3 vaccine types among study patients.

Vaccine seroresponse occurred in 87% of BNT162b2/Pfizer, 96% of mRNA-1273/Moderna, and 37% of Ad26.COV2.S/Janssen recipients (Table S1). Patients without seroresponse were assumed to maintain the absence of seroresponse between the last titer assessment and the 74th day after vaccine series completion. Among those without seroresponse, the median duration of this period was 19.5 [IQR, 12-29], 24.5 [IQR, 12-34], and 16 [IQR, 9-20] days for BNT162b2/Pfizer, mRNA-1273/Moderna, and Ad26.COV2.S/Janssen recipients, respectively (Fig S2).

At titer ≥2 U/L, seroresponse was slightly lower for all vaccine types, most notably Ad26.COV2.S/Janssen. When limiting to the first SAb-IgG titer ≥14 days after vaccine series completion, seroresponse rate was significantly lower only among Ad26.COV2.S/Janssen recipients (Table S1). Vaccine type, older age, non-Black and non–Native American race, immune-modulating medications, history of transplantation, and lower serum albumin were associated with lower likelihood of seroresponse (Fig 1 ).

Figure 1

Multivariable regression of clinical characteristics associated with SARS-CoV-2 vaccine response. Response defined as SAb-IgG titer ≥1 U/L measured 14-74 days after vaccine series completion. The association for number of comorbidities is expressed per additional comorbidity. Peritoneal dialysis is compared to hemodialysis (either in-center or home). Analysis was performed with multivariable log Poisson regression with robust variances. See Table 1 notes for abbreviations and definitions.

Among maintenance dialysis patients, mRNA vaccines against SARS-CoV-2 elicited seroresponse in the vast majority, consistent with prior reports.1, 2, 3, 4, 5, 6 In contrast, seroresponse to Ad26.COV2.S/Janssen was low, consistent with an earlier small study, suggesting that maintenance dialysis patients should receive mRNA-based SARS-CoV-2 vaccines, particularly given their high morbidity and mortality from COVID-19.

The low seroresponse rate to Ad26.COV2.S/Janssen is concerning because postvaccination SAb-IgG titers correlate with protection from COVID-19, possibly via direct neutralization of the spike protein. Of note, as a single-dose regimen, response to Ad26.COV2.S/Janssen was assessed 3-4 weeks earlier relative to the initial vaccine dose than response to mRNA vaccines. However, longer-term data elsewhere do not indicate increased response over time. Thus, even allowing for possible later increase in seroresponse, the Ad26.COV2.S/Janssen vaccine appears less effective than mRNA vaccines among maintenance dialysis patients.

The difference between BNT162b2/Pfizer and mRNA-1273/Moderna may reflect differences in dosage (100 vs 30 μg of mRNA content, respectively), or, given the earlier availability of BNT162b2/Pfizer, unaccounted-for confounding factors. Admittedly, the SAb-IgG titer needed for protection from COVID-19 and the role of vaccine-induced cellular immunity remain uncertain, issues that are complicated by emerging variants. Other than vaccine type, predictors of vaccine nonresponse were largely factors related to potential immunocompromise. ,

Our study limitations include potential selection bias and unaccounted-for confounders. We did not examine breakthrough infections, which are a growing concern. Also, although assessing SAb-IgG titer ≥14 days after completion of vaccine series meets the current definition of “fully vaccinated,” there remains a difference in timing relative to the initial dose between 1- and 2-dose regimens.

In conclusion, among maintenance dialysis patients, mRNA vaccines are associated with greater seroresponse and therefore should be preferred. Further study is needed on the durability of this seroresponse; its correlation with breakthrough infection, morbidity, and mortality; and the role of additional vaccine doses, particularly among Ad26.COV2.S/Janssen vaccine recipients.