P-643. Incidence and Clinical Characteristics of Invasive Group A Streptococcal Infections in Underhoused Adults in Toronto, Canada

Abstract Background Post-pandemic increases of invasive group A streptococcal disease (iGAS) have been reported in many areas of the world; increased risk associated with illicit intravenous (IV) drug use has also been identified. Methods Since 1995, the Toronto Invasive Bacterial Diseases Network (TIBDN) has conducted prospective, population-based surveillance for iGAS in residents of Toronto/Peel Region (pop, 4.5M) in Canada. Homeless adults admitted to hospitals in the surveillance area are counted as residents. General and homeless population estimates were taken from Statistics Canada and published literature (doi:10.1136/bmjopen-2019-030221). Canada's National Microbiology Laboratory performs emm typing. Results In 2022/23, 88 iGAS cases (14% of all iGAS cases, 17% of adult iGAS) occurred in homeless persons; all were adults. Estimated iGAS incidence in homeless adults was 210/100,000/yr, versus 5.4/100,000/yr in other adults. Homeless persons with iGAS were younger than other adults (median age 47 v. 59 yr, P< .001); 70% were male (v. 63% in other adults, P=0.2). Homeless adults were more likely than other adults to be smokers (53% v. 27%, P< .001), to use IV drugs (46% v. 10%, P< .001), to have non-intact skin (43% v. 27%, P< .001) and to report recent soft tissue trauma (27% v. 17 %, P< .001). Compared to other adults, homeless adults were more likely to have comorbidities (90% v. 79%, P< .001), but less likely to be immunocompromised (3% v. 19%, P< .001). Presentations differed in homeless versus other adults (Table 1). 16 (18%) homeless adults required ICU admission, 10 (11%) mechanical ventilation, and 5 (8.5%) died. After age adjustment, outcomes did not differ between homeless and other adults. The median hospital length of stay was 8.5 days (IQR: 4-22) for homeless adults, and 8 days (IQR: 5-18) for other adults (P=0.7). The distribution of emm types of isolates in homeless and other adults is shown in Figure 1. iGAS in homeless adults was less likely to be caused by isolates of emm 1 and 12, and more likely to be caused by isolates of emm 49 and 74. Conclusion Homeless persons are at very high risk of iGAS, with IV drug use and skin integrity issues contributing. Outcomes of iGAS are similar to other adults. Differences in the emm types of isolates may be relevant to future vaccine program planning. Disclosures Allison McGeer, MD, AstraZeneca: Honoraria|GSK: Honoraria|Merck: Honoraria|Moderna: Honoraria|Novavax: Honoraria|Pfizer: Grant/Research Support|Pfizer: Honoraria|Roche: Honoraria|Seqirus: Grant/Research Support|Seqirus: Honoraria