MO699: Investigating Longer Term Antibody Response Following Covid-19 Vaccination in Patients Receiving Peritoneal Dialysis—a Single-Center Observational Study
Authors: Chinnadurai Rajkumar , Ramgobin Chittesh , Lin Henry Wu Hon , Hayes Emma , Collier Joanne , Lewis David , Poulikakos Dimitrios 
Published: May 2022

Abstract

BACKGROUND AND AIMS
Individuals with end-stage kidney disease (ESKD) have a greater susceptibility towards coronavirus disease 2019 (COVID-19) infection compared to those without chronic kidney disease or ESKD, and these patients are more vulnerable to poor clinical outcomes. The introduction of COVID-19 vaccination programs displayed efficacy to improving clinical outcomes. A study based in the UK reported excellent humoral responses to the Pfizer BNT162b2 vaccine, but suboptimal responses to the Oxford AstraZeneca ChAdOx1-nCoV-19(AZD1222) vaccine amongst hemodialysis patients. High rate of humoral responses to two doses of the COVID-19 vaccination has been reported within small cohorts of peritoneal dialysis (PD) patients 3 to 8 weeks post vaccination, whilst one study confirmed maintenance of significant humoral responses 6 months post vaccination with the Pfizer BNT162b2 vaccine. Our study aimed at evaluating longer-term antibody responses—6 months after a two-dose regimen of the Pfizer BNT162b2 and Oxford AstraZeneca ChAdOx1-nCoV-19 (AZD1222) vaccines in patients receiving PD.

METHOD
This is a single-center observational study conducted for PD patients who were offered both doses of the COVID-19 vaccine [either Pfizer BNT162b2 or Oxford AstraZeneca ChAdOx1-nCoV-19(AZD1222)] since universal introduction of the vaccination program in our local area in December 2020. COVID-19 antibody testing was performed using the Siemens’ immunoassay targeting the spike protein S1 RBD (an index ≥ 1.0 was deemed as a positive result) between October and November 2021. Demographic and baseline clinical data were collected for each patient, and analysis focused on comparing the characteristics between PD patients with positive and negative COVID-19 antibody statuses. Statistical analysis was performed using SPSS version 24.

RESULTS
Eighty-six patients were included in this study. The median age was 62 years (47–71) with a predominance of males (61.6%) and Caucasian ethnicity (75.6%). The majority of patients have hypertension (84.8%) with 38% having a history of cardiovascular disease and 34% being diabetic. Ten patients (11.6%) previously received a kidney transplant with 7 patients (8.2%) currently on immunosuppressive treatment, and 15 patients (17.4%) previously receiving such treatments. A total of 81 patients received both doses of the COVID-19 vaccine, of which 57 (70.4%) received Pfizer BNT162b2, 16 (19.7%) received Oxford AstraZeneca ChAdOx1-nCoV-19 (AZD1222) and the type of vaccine was unknown in 8 patients (9.9%). A total of 72 patients were COVID-19 antibody tested between October and November 2021 in which 68 (94.4%) had a positive antibody and 4 (5.6%) had a negative antibody test. The median time between first dose of the COVID-19 vaccination and antibody testing was 9 (8.6–9.5) months and the median time between second dose of the COVID-19 vaccination and antibody testing was 6.3 (5.8–6.7) months. Comparing the demographic and clinical characteristics between patients with positive and negative antibodies, a higher proportion of patients with history of receiving immunosuppression (currently or previously; P = 0.004) had a negative antibody status despite receiving two doses of COVID-19 vaccination. There were no further significant differences observed. Full study results are presented in Tables 1 and 2.

CONCLUSION
In our cohort of PD patients, detectable humoral response to COVID-19 vaccination was sustained 6 months following vaccination irrespective of the type of vaccination received. A higher proportion of patients with a history of receiving immunosuppression (current or past) had a poor antibody response following COVID-19 vaccinations, highlighting the importance of considering focused COVID-19 vaccination strategies in the context of immunosuppression.