BackgroundPatients with autoimmune connective tissue disease (CTD) and systemic vasculitis (SV) often require aggressive immune-modulating therapy to prevent organ damage. This however increases the risk for common and uncommon infections.ObjectivesTo compare the temporal rates and associated mortality of hospitalisation with opportunistic infections (OI) for CTD and SV patients in Western Australia between 1985 and 2015.MethodsAll patients hospitalized in Western Australia in the period 1985-2015 with ≥ 2 ICD based diagnostic codes for SLE (n=1432), other CTD (o-CTD; incl DM/PM, systemic sclerosis, Sjogren’s syndrome; n=2161) and Systemic vasculitis (SV; n=1599) and a microbiologically confirmed OI (Mycobacterial, Fungal and viral infections) were included. Descriptive data are given as median (IQR) and frequency (%). Incidence rates per 1000 person years (IR) were calculated during 100.410 person years.ResultsOI occurred in 12.4 % of lupus, 11.5% of SV and 10.4% of o-CTD patients (p=0.72), but overall IR rates for OI were higher for lupus patients (9.87, CI 5 .49-15.76) than for SV (5.94, CI-2.81-10.24) and o-CTD patients (3.40, CI 1.62-7.23). However, whereas the IR for OI in lupus decreased over time, the IR increased for SV and o-CTD patients (Figure 1). Viral infections were the most frequent specific OI followed by tuberculosis and mycotic infections. Cryptococcal infections were observed in lupus patients only and the limited cases of pneumocystis occurred predominantly in SV patients with no cases observed after 2000 (Figure 2). In hospital mortality during OI admission was 11.5% for SV, 5.6 % for lupus and 3.5% for o-CTD patients (p=0.004).Figure 1.Figure 2.ConclusionHospitalization rates for OI have decreased for lupus patients especially since 2005, whereas viral and mycotic OI rates have increased for both SV and o-CTD patients. Hospitalization for OI associated with significant case fatality in especially SV patients, indicating a need for increased prevention of OI.