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Background Hepatitis C virus (HCV) elimination among gay and bisexual men (GBM) living with HIV is feasible in many high-income countries. There is concern that risk behaviours following treatment may lead to reinfection and adversely impact HCV elimination goals. We examined risk behaviours prior to and following HCV treatment commencement among sexually active GBM living with HIV. Methods Data were drawn from co-EC, a prospective study aiming to treat and eliminate HCV among people living with HIV. Pre and post-HCV treatment commencement changes in self-reported sexual and injecting drug-related behaviours among sexually active GBM attending primary and tertiary care clinics in Melbourne were assessed using McNemar’s test. Modified Poisson regression with robust variance was used to examine factors associated with risk behaviours following treatment commencement. Results Of 120 males who completed both a pre and post-treatment commencement questionnaire, 90 reported ≥1 male sex partner before or after treatment commencement. Among these 90 sexually active GBM, there was no significant change pre- to post-treatment in condom-less anal intercourse with casual partners (52.5%/56.6%, p 0.513) or injecting drug use (41.2%/45.9%, p 0.344), but a significant decrease in group sex (34.4%/21.1%, p 0.011). Post-treatment commencement, condom-less intercourse (adjusted prevalence ratio (aPR) 1.80, 95%CI 1.07–3.03, p 0.026) and group sex (aPR 4.53, 95%CI 1.76–11.67, p 0.002) was highest amongst those who had reported these behaviours pre-treatment. Post-treatment commencement, injecting drug use was associated with the use of crystal methamphetamine during follow-up (aPR 4.36, 95%CI 1.27–14.94, p 0.019). Conclusion HCV-related risk behaviours were common among sexually active GBM before and after HCV treatment and primarily occurred among the same men. There was no significant evidence of increasing risk behaviour following treatment. More frequent post-treatment HCV testing may be justified among GBM engaging in these behaviours to identify potential HCV reinfection and provide prompt re-treatment to prevent further transmission. Disclosure No significant relationships.

Introduction HIV notifications have increased significantly in Victoria since 2000. The majority of these are among men who have sex with men (MSM). Chlamydia, gonorrhoea and syphilis notifications have also increased among MSM in Victoria and reinfection occurs in approximately 15%–30% of MSM retested after a positive diagnosis of syphilis, chlamydia or gonorrhoea. Sexually transmissible infections (STI) have been associated with an increased risk of HIV acquisition. We aimed to test whether repeat infection increased the risk of HIV infection among MSM. Methods A retrospective analysis of sentinel surveillance data was conducted. HIV negative MSM who attended three high case load clinics in Victoria from 2007 to 2014 with two or more HIV tests were eligible for inclusion. STI diagnosis and behavioural exposures were lagged to a patient’s prior test event and an individual level discrete-time survival analysis using generalised linear modelling estimated the cumulative effect of repeat STI diagnoses on HIV diagnosis risk. Results 8941 individuals were included in the analysis among whom 2.5% (n=227) were diagnosed as HIV positive. After adjustment for number of sexual partners and condom use in the previous six months, repeat rectal gonorrhoea infection (adjusted hazard ratio [aHR]: 6.24, 95% confidence interval [95% CI]: 2.68–14.50), single-event rectal gonorrhoea (aHR: 2.09, 95% CI: 1.15–3.79), rectal chlamydia (aHR: 1.89, 95% CI: 1.12–3.18) and syphilis (aHR: 1.99, 95% CI: 1.00–3.96) infections were associated with an increased risk of HIV diagnosis. Repeat rectal chlamydia infection (aHR: 1.62, 95% CI: 0.73–3.59) and repeat syphilis infection (aHR: 0.93, 95% CI: 0.11–7.65) were not associated with an accumulated increased risk of HIV diagnosis. Conclusion In addition to increased risk due to a single STI, repeat rectal gonorrhoea infection was strongly associated with an accumulated increased risk of HIV diagnosis. These findings suggest MSM with repeat rectal gonorrhoea infection represent a higher risk group for whom preventive interventions are encouraged.