MO191: Humoral Immune Response of the Additional Chadox1 NCOV-19 Vaccine Following a Two-Dose Inactivated Whole-Virus SARS-COV-2 Vaccination in Patients on Dialysis
Authors: Kitpermkiat Rungthiwa , Bruminhent Jackrapong , Setthaudom Chavachol , Chuengsaman Piyatida , Kiertiburanakul Sasisopin , Malathum Kumthorn , Assanatham Montira , Nongnuch Arkom , Phuphuakrat Angsana , Chaumdee Pongsathon , Janphram Chitimaporn , Thotsiri Sansanee , Boongird Sarinya 
Published: May 2022

Abstract

BACKGROUND AND AIMS
Patients with end-stage kidney disease (ESKD) are at risk of coronavirus disease 2019 infection and its associated complications. A previous study demonstrated that patients with ESKD on dialysis generated suboptimal humoral immune response (HIR) and lower seroconversion rate after two-dose inactivated severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccination as compared to healthy individuals. In this study, we examined HIR of the additional dose of ChAdOx1 nCoV-19 vaccine following a standard two-dose inactivated whole-virus SARS-CoV-2 vaccination in patients on dialysis, and compared to those of healthy controls.

METHOD
We recruited 59 patients with ESKD [31 patients on haemodialysis (HD) and 28 on peritoneal dialysis (PD)) and 16 healthy controls who received two doses of inactivated SARS-CoV-2 vaccine (V2) from Ramathibodi hospital and Banphaeo General Hospital, Bangkok, Thailand, from July 2021 to September 2021. All participants were administered a third dose of the ChAdOx1nCoV-19 vaccine (V3) with a 6-week interval between the V2 to V3. HIR was measured 2 weeks after V2 and V3 using SARS-CoV-2 immunoglobulin G (IgG) assay, which detects antibodies against the S1 receptor-binding domain (RBD) of the SARS-CoV-2 spike protein. Median anti-RBD IgG titer and seroconversion rate, defined as anti-RBD IgG titre ≥ 7.1 BAU/mL, were compared among ESKD patients and to those of healthy controls using the Kruskal–Wallis H test and the chi-squared test, respectively.

RESULTS
Baseline characteristics of patients on HD, PD and healthy controls are shown in Table 1. Demographic characteristics and baseline laboratory parameters were comparable between the HD and PD groups, except for a lower mean serum albumin level in the PD group (P &lt; .001). None of the healthy controls were immunocompromised or receiving immunosuppressive therapies.
At 2 weeks after V3, the median anti-RBD IgG titres were significantly increased in all groups compared to those levels after V2 (85[33–412] versus 1566 [861–3083] BAU/mL for patients on HD, 81 [15–144] versus 913 [293–1359] BAU/mL for patients on PD and 250 [92–603] versus 2210 [1531–2782] BAU/mL for healthy controls; P &lt; .001 for all groups). Comparing antibody levels between groups after V3, patients on PD generated significantly lower anti-RBD IgG titer than patients on HD (P = .02) and healthy controls (P &lt; .01) (Figure 1A). The seroconversion rate of the HD and PD groups improved from 94% and 82% after V2 to 100% after V3 in both groups (P = .16 and P = .03, respectively) (Figure 1B). All patients on dialysis who had anti-RBD IgG &lt; 7.1 BAU/mL after V2 (7/59 patients) seroconverted after the additional dose of ChAdOx1 nCoV-19 vaccine.

CONCLUSION
We suggest that an additional ChAdOx1 nCoV-19 vaccine after a primary two doses inactivated SARS-CoV-2 vaccination could improve seroconversion rate and magnitude of humoral immune response in patients on dialysis. The durability of the immune response to this vaccination regimen requires further study.