Humoral response of the mRNA-1273 SARS-CoV-2 vaccine in peritoneal dialysis patients.

To the editor:

Patients with end-stage kidney disease on peritoneal dialysis are known to have an altered cellular and humoral immunity evidenced by the reduced response they have to several vaccines, such as the hepatitis B or influenza vaccine, albeit their response rate is slightly higher than that of patients on hemodialysis.

Although patients on peritoneal dialysis have a reported lower prevalence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection than patients on in-center hemodialysis, probably because of their ability to self-isolate appropriately, they still have higher mortality and longer hospital admissions than the general population. Currently, there is a lack of data on this population’s response to SARS-CoV-2 vaccines. As mRNA vaccines have data of higher potency in comparison to other types of vaccines, this class has been suggested as the preferred one until more data on their response are available.

We evaluated the humoral response of 34 patients from our peritoneal dialysis unit at the Hospital Clínic of Barcelona. This population was immunized with 2 doses of the mRNA-1273 vaccine separated by a 28-day interval as specified by the manufacturer. Antibody titers were quantified with the Siemens Healthineers Atellica IM SARS-CoV-2 IgG assay, which detects IgG antibodies to the receptor-binding domain of the S1 spike antigen of SARS-CoV-2, at 3 moments: before administering the first dose, before administering the second dose, and 3 weeks after the latter (see Figure 1 ).

Figure 1

IgG antibodies to the receptor-binding domain of the S1 spike antigen of severe acute respiratory syndrome coronavirus 2 (anti-S1 IgG) titer at baseline and after each dose of the mRNA-1273 vaccine.

Two of 34 patients had positive serology at baseline and were thus excluded from the analysis of seroconversion after vaccination. From the remaining 32, 20 (62.5%) generated detectable IgG antibodies to the receptor-binding domain of the S1 spike antigen of SARS-CoV-2 after only 1 dose whereas 11 (34.38%) responded only after 2 doses were administered. Demographic characteristics, comorbidities, and laboratory parameters were analyzed, seeking correlation between them and either the humoral response intensity (IgG antibodies to the receptor-binding domain of the S1 spike antigen of SARS-CoV-2 titers) or its velocity (seroconversion after 1 dose vs. seroconversion after 2 doses). However, no statistically significant differences were observed between groups (see Table 1 ). Only 1 patient did not seroconvert after completing vaccination, and, although the patient was a 77-year-old diabetic obese man, we did not find any compelling reason for this lack of response.

Table 1

Clinical characteristics of patients on peritoneal dialysis who seroconverted after the first or second dose of the mRNA-1273 vaccine

Characteristic	Seroconverted after only the first dose (n = 20 [62.5%])	Seroconverted after the second dose (n = 11 [34.38%])
Age, yr	62.2 ± 16.0	65.7 ± 16.3
Male sex	9 (45)	2 (18.2)
Diabetes	3 (15)	3 (27.3)
HbA1C	5.5 ± 0.8	5.6 ± 0.9
Body mass index, kg/m2	26.4 ± 4.2	26.2 ± 6.5
Overweight	7 (35)	2 (18.2)
Obesity	6 (30)	2 (18.2)
Immunosuppressive therapy	2 (10)	2 (18.2)
Charlson index	4.95 ± 2.16	5.18 ± 2.48
Albumin, g/dl	4.00 ± 0.33	3.92 ± 0.56
C-reactive protein, mg/dl	0.57 ± 1.11	0.62 ± 1.15
Vitamin D3, ng/ml	19.35 ± 10.87	18.57 ± 5.67
Lymphocytes, ×106	1450 ± 79	1254.55 ± 628
Hemoglobin, g/dl	11.82 ± 1.79	10.97 ± 1.69
Dialysis vintage, mo	64.48 ± 122	26.49 ± 20
Weekly Kt/V	2.02 ± 0.43	1.88 ± 0.41
Anti-S1 IgG titer, U/ml	17.53 ± 32.89	76.81 ± 70.45

Anti-S1 IgG, IgG antibodies to the receptor-binding domain of the S1 spike antigen of severe acute respiratory syndrome coronavirus 2; HbA1C, glycated hemoglobin.

Data are expressed as mean ± SD or n (%).

SARS-CoV-2 vaccination is of particular importance in high-risk populations such as patients on peritoneal dialysis. The 97% of response observed, high in comparison to kidney transplant recipients (25%) and similar to patients on hemodialysis (90%), reinforces the idea that this population should be vaccinated as soon as possible as most of them seroconvert and are therefore likely protected from severe coronavirus disease 2019.