Abst0437 #ACR21 @RheumNow factors assoctd w/poor response to mRNA Covid-19 vaccine in rheum pts Rx w/Rituxan: ⬆️ exposure to RTX over time, ⬇️ IgG levels prior to RTX, short interval btw RTX course & BNT162b2 vacc. RA highest&ANCA-vasculitis lowest probability for a + response. https://t.co/DsrJBlNvr7