AB1293 OMICRON BREAKTHROUGH INFECTIONS AMONG RITUXIMAB AND NON-RITUXIMAB TREATED PATIENTS WITH AUTOIMMUNE INFLAMMATORY RHEUMATIC DISEASES: A MULTICENTER CONTROLLED STUDY

Background Little is known about the efficacy of booster COVID-19 vaccination in rituximab (RTX)-treated patients with autoimmune inflammatory rheumatic diseases (AIIRD). Objectives To estimate breakthrough infection rate AIIRD treated RTX compared to other therapies and immunocompetent controls. Methods This observational multi-center study investigated humoral response (anti-S1/S2 IgG) BNT162b2 mRNA RTX-treated vs non-RTX controls for 18 months. investigate impact 3rd 4th vaccine doses, a survival analysis was applied. Predictors time-to-infection were analyzed using multivariate Cox proportional hazard model. Results A total 115 patients, 590 non-RTX-treated 121 included analysis. received more doses than controls, median 3 (range 2-4) 2 (2-4), respectively, p<0.0001; 53.82% (n=402) 32.8% (n=41), 3.88% (n=29) 2.4% (n=3), p <0.0001 both comparisons. Patients within one year from last (n=84) had lowest anti-S1/S2 IgG level following each others highest since start campaign general 32.26% (40/124), 27.29% (170/623), 28.8% (36/125), p=0.2206. During Omicron surge, time-to shorter among irrespective type anti-rheumatic (Figure 1A). In Cox-regression model, time interval between treatment associated lower risk contract COVID-19, HR 0.998 (95% CI 0.997-1), p=0.0298 1B) For 30-day date, declined 0.941-fold. The after adjustment age S1/S2 serology 2.077, 95% 1.056-4.086, p=0.0342. Reassuringly, no cases severe or COVID-19-related mortality reported during surge. Conclusion found comparable rates vaccinated immunomodulators. Recent exposure predisposed infection. REFERENCES: NIL. Acknowledgements: Disclosure Interests None Declared.