The goal of this multicentre observational study is to compare the safety and effectiveness of rituximab biosimilars to the originator in Canadian patients with Granulomatosis with Polyangiitis (GPA) and Microscopic Polyangiitis (MPA), two main forms of ANCA-associated vasculitis (AAV). The main questions it aims to answer are: * Is there a difference in vasculitis control between originator and biosimilar rituximab? * Is there a difference in adverse effects between originator and biosimilar rituximab? * In the Canadian healthcare context, are wait times to receive approval (financial coverage) for rituximab shorter for biosimilars compared to originators? Investigators will perform study assessments (including recording disease activity, damage, and adverse events) at the time of participants' usual clinical care visits, at regular intervals for 2 years after starting rituximab (for induction or maintenance treatment) or switching from an originator to a biosimilar as part of their usual care. Researchers will compare outcomes among participants who have received rituximab originators (from 2018 onwards) or biosimilars as part of their usual care, to see if there are differences in relapses, remission rates, damage, serious infections, serious adverse events, and treatment approval wait times.
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Proportion of participants with a relapse
Timeframe: 6 months
Time to relapse
Timeframe: From Month 0 until date of first relapse, assessed up to 24 months