Humoral Response to BNT162b2 mRNA Covid19 Vaccine in Peritoneal and Hemodialysis Patients: a Comparative Study

Abstract Introduction Generalized immunization against COVID19 has become the cornerstone in prevention of severe acute respiratory syndrome associated with this pandemic. Maintenance dialysis patients (MDP) are at higher risk of both exposure and mortality from the disease. Efficacy and security of BNT162b2 vaccine is well documented for the general population, but not in MDP, particularly in peritoneal dialysis (PD) patients. This study aims to compare humoral response between hemodialysis (HD) and PD patients. Materials and Methods Observational prospective study including MDP on HD or PD program from a Portuguese middle-sized Nephrology Center, who received BNT162b2 vaccine. Specific anti-Spike IgG was measured as arbitrary units per milliliter (AU/mL) on two separate occasions: 3 weeks after the first dose and 3 weeks after the second. The two modality groups were compared both for absolute value and number of non-responders (NR) after both inoculations. Demographic data was also compared. Results Of 73 patients enrolled, 67 were eligible for the final study: 42 HD and 25 PD patients. PD group developed significantly higher antibody titers in both inoculations: first dose with Med 5.44 vs 0.99 (p<0.01) and second dose with Med 170.43 vs 65.81 (p<0.01). HD status was associated with NR after the first dose (Phi=0.383; p<0.01), but not after the second (p=0.08). Age, Charlson comorbidity index and dialysis vintage were lower in the PD group (p<0.01; p=0.02; p<0.01, respectively). Conclusion This study demonstrated a better humoral response to immunization with BNT162b2 in PD patients, when compared to HD patients, after each of the two recommended inoculations. Both groups showed substantial humoral response after just one dose of the vaccine. Older age and higher comorbidity burden may explain the relative immunogenicity deficit, probably in a superior degree comparing with age matched healthy population. What is already known about this subject Maintenance hemodialysis patients have lower humoral response to BNT162b2 mRNA COVID19 vaccine when compared to the general population; Maintenance dialysis patients are at high risk of exposure to COVID19 in addition to a more severe course of the disease; What this study adds Maintenance peritoneal dialysis patients have better humoral response with BNT162b2 when compared to those on hemodialysis; There is a substantial humoral response after a single dose of the vaccine for both hemodialysis (50%) and peritoneal dialysis (88%) patients. What impact this may have on clinical practice or policy Protocols for follow-up measures, including extra inoculations, might have to be considered for hemodialysis patients; Peritoneal dialysis patients should be promptly immunized in all centers, rejecting constraints regarding lower effectiveness or yield.