Similar humoral immune responses in peritoneal dialysis and haemodialysis patients after two doses of the SARS-CoV-2 vaccine BNT162b2

Humoral immune response after Covid-19 infection in haemodialysis (HD) patients is similar compared to healthy controls, ¹ but lower following BNT162b2 vaccination. ² We assessed post-vaccination anti-SARS-CoV-2 spike IgG in peritoneal dialysis (PD) and HD patients by quantitative enzyme-linked immunosorbent assay (QuantiVac, EUROIMMUN, Germany; sensitivity: 93.2%, specificity: 99.8%) after first and second BNT162b2 vaccination. Nineteen healthcare professionals without comorbidities or long-term medication served as controls (Table 1). Prior SARS-CoV-2 infections were excluded by the absence of anti-SARS-CoV-2 nucleocapsid IgG antibodies.

Table 1.

Demographic description.^a

	PD, n = 30			HD, n = 30		Control, n = 19
Age in years (mean)	69.9 ± 12.5			74.1 ± 9.2		44.4 ± 9.9b
Female	14 (47)			12 (40)		11 (58)
Time on dialysis in years (mean)	2.6 ± 3.2			5.5 ± 4.1		–
Mean time anti-spike IgG after second dose (days)	21.2 ± 0.9			23.8 ± 3.5		65.3 ± 8.6b
Dialysis modality	NIPD	CAPD	APD	HD	HDF	–
	10 (33)	16 (53)	4 (13)	28 (93)	2 (7)	–
Underlying renal disease
Hypertensive nephropathy	6 (20)			11 (37)		–
Glomerulonephritis	7 (23)			5 (17)		–
Diabetic nephropathy	6 (20)			4 (13)
Cardiorenal syndrome	5 (17)			3 (10)		–
Congenital disease	3 (10)			1 (3)		–
Tubulointerstitial disease	1 (3)			0 (0)
Other	2 (7)			6 (20)		–
Immunosuppressive medication
GC ointments	3 (10)			0 (0)		–
Inhalated GC	4 (13.3)			0 (0)		–
Oral GC	3 (10)			1 (3)		–
MMF + GC	1 (3)			0 (0)		–
MMF + TAC + GC	2 (7)			0 (0)		–

PD: peritoneal dialysis; NIPD: nocturnal intermittent PD; CAPD: continuous ambulatory PD; APD: automated PD; HD: haemodialysis; HDF: haemodiafiltration; MMF: mycofenolate mofetil; GC: glucocorticoid; TAC: tacrolimus.

^a Values are depicted as absolute numbers with percentage in brackets, if not otherwise stated.

^b p < 0.05, t test between dialysis patients and controls.

About half of all PD (n = 13) and HD (n = 15) patients had detectable anti-spike IgG after the first vaccination and this rate increased to 90% (n = 26) and 100% (n = 30) after the second vaccination, respectively (Figure 1). Median anti-spike IgG increase significantly 15-fold in the PD and 10-fold in HD group (p < 0.0001, Wilcoxon test) and were not different between groups. Median anti-spike IgG in dialysis patients were within the range of healthy controls, but none of the controls were below the overall 25% percentile (85 RU/mL) as compared to 27% of HD and 37% of PD patients (p = 0.017 and 0.0017, respectively, Fisher’s exact test). Controls were younger but tested later after the second vaccination (Table 1). Patients receiving glucocorticoids tended to show less frequent seroconversion after the first dose (25%) and lower median anti-spike IgG amounts after first and second dose (2.69 and 83.3 RU/mL, respectively).

Figure 1.

Anti-SARS-CoV-2 spike protein IgG levels. Responses 3 weeks after the first (bright green dots) and second (dark blue dots) vaccination with BNT162b2 in HD patients, PD patients or controls. Black bars indicate the median values, the dotted lines represent the lower cut-off (11 RU/mL) and the upper limit for quantification by the QuantiVac test (dots depicted on the upper limit are equal or above 120 RU/mL). Wilcoxon signed-rank test for paired samples and Mann–Whitney U test for comparison between groups.HD: haemodialysis; PD: peritoneal dialysis.

In summary, most HD and PD patients developed detectable humoral responses after two BNT162b2 vaccinations and reached comparable median anti-spike IgG levels. However, individual patients had inferior responses compared to healthy controls and may require additional booster doses to achieve long-term immunity. ^3,4