Purpose:
The aim of this study is to assess long-term immunogenicity of the recombinant adenoviruses 26 and 5 vector-based COVID-19 vaccine Gam-COVID-Vac (Sputnik V, developed by N. F. Gamaleya National Research Centre, Russia) in patients receiving maintenance hemodialysis (HD) compared to healthy subjects.

Materials & methods:
A prospective cohort study included patients treated with maintenance HD (n=23) and healthy volunteers (n=28). The levels of anti-severe acute respiratory syndrome coronavirus-2 specific IgG as well as specific T-cell responses were quantified in all participants at two time points: one and six months after complete vaccination. All participates were adults, had been vaccinated twice with Gam-COVID-Vac and had no prior history of confirmed COVID-19.

Results:
In both groups, IgG levels decreased from month one to six, however, antibodies did not decline more rapidly in HD group (analysis of variance p=0.7214 for the “time×group” interaction, non-adjusted model). At the end of the study, 48.0% of non-HD and 67.0% of HD participants showed T-cell positivity. T-spot counts dropped over time in non-HD controls, but not in HD subjects (p=0.0080 and p=0.1800, respectively).

Conclusions:
Patients receiving HD maintain significant long-term humoral response after Gam-COVID-Vac vaccination, which is comparable to that in subjects with normal kidney function. Cellular response turned up to be more sustained over time in HD group.