Humoral immune response to an mRNA-1273 booster after chAdOx1-nCoV-19-priming among patients undergoing hemodialysis

OBJECTIVES: Patients who are undergoing dialysis due to end-stage kidney disease are susceptible to greater coronavirus disease 2019 (COVID-19) complications. While vaccination is seen as the most effective tactic against COVID-19, the dialysis population usually has impaired immune responses to vaccination. Owing to the global vaccine supply shortage in the early phase of the COVID-19 pandemic, hemodialysis patients in Taiwan were administered homologous ChAdOx1 nCoV-19/ChAdOx1 nCoV-19 at 12-week intervals, with a third booster shot of mRNA-1273 given 12 weeks after the second dose. We assessed the antibody responses of these patients to this extended-interval dosing protocol. MATERIALS AND METHODS: A total of 168 hemodialysis patients (mean age: 67 ± 13 years) without prior COVID-19 infection were vaccinated between June 16, 2021, and January 5, 2022, and followed until February 10, 2022. The primary outcome was seroconversion with an antispike immunoglobulin G (IgG) antibody level ≥50 arbitrary units (AU)/mL at 4 weeks after the administration of an mRNA-1273 booster shot. The secondary outcome was the level of antispike IgG antibodies. Multivariable linear regression models were used to evaluate the associations between the baseline characteristics and the antispike IgG level. RESULTS: A total of 163 (97.0%) patients reached the primary endpoint, with antibody levels after the third booster dose of mRNA-1273 being significantly higher than those after the second dose of ChAdOx1 nCoV-19 (median IgG titer 12,007 [4394–23,860] vs. 846 [interquartile range 295–2114] AU/mL; P < 0.001). Patients who were male, older, had a higher body mass index, had a lower total lymphocyte count, and used immunosuppressants had lower antibody levels. CONCLUSION: A third booster dose of mRNA-1273 after two consecutive priming doses of ChAdOx1 nCoV-19 with extended intervals resulted in adequate humoral immune responses among hemodialysis patients.