Changes in serious infection and mortality among patients with ANCA-associated vasculitis during the COVID-19 pandemic: an interrupted time-series analysis of J-CANVAS

Objectives: In antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis, infection risk exceeds that of the general population, and infection is a leading cause of death.However, the impact of the COVID-19 pandemic on serious infections and mortality in this population remains uncertain.Methods: This observational study used data from the nationwide registry in Japan (Japan Collaborative Registry of ANCA-Associated Vasculitis), which includes patients with newly diagnosed and relapsed ANCA-associated vasculitis from 29 sites between January 2017 and March 2023.The primary outcome was serious infection requiring hospitalisation; the secondary outcome was all-cause mortality.The impact of COVID-19 was estimated using an interrupted timeseries analysis, with the boundary between April and May 2020 as the change point, following the first declaration of a state of emergency in Japan.Monthly incidence rates were modelled using segmented Poisson regression.Rate ratios (RRs) for level and slope changes with 95% CI were reported.Several sensitivity analyses were performed.Results: Among 1064 patients, total follow-up was 37,535 person-months; 205 serious infections and 96 deaths occurred.For serious infection, the level-change RR was 0.54 (95% CI: 0.31-0.94)and the slope-change RR was 1.01 (0.98-1.04).For all-cause mortality, the level-change RR was 0.35 (0.12-0.98) and the slope-change RR was 1.001 (0.94-1.06).Findings were robust across sensitivity analyses.Conclusions: Immediately after the onset of the COVID-19 pandemic, a clear reduction in serious infections and mortality was observed without major changes in patient characteristics.These findings may reflect the impact of social and personal infection control measures. WHAT IS ALREADY KNOWN ON THIS TOPICSeasonal infectious diseases declined in the general population during the COVID-19 pandemic, but whether similar changes occurred in serious infections and mortality among patients with antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis was unknown. WHAT THIS STUDY ADDSIn a nationwide Japanese registry (Japan Collaborative Registry of ANCA-Associated Vasculitis), serious infections and allcause mortality in ANCA-associated vasculitis declined immediately after the onset of the COVID-19 pandemic.