P512 Quantifying sexual mixing by HIV status and pre-exposure prophylaxis (PrEP) use among men who have sex (MSM) with men
Year: 2019
Type: conference-abstract
Abstract: Background Existing measures of preferential partner selection do not account for attribute-concordance by chance. We quantified network-level sexual mixing by HIV status and PrEP use using a balancing partnership approach. Methods Data were from Engage, a cross-sectional survey of MSM ≥16 year-old in three Canadian cities (2017–2018). MSM with ≥1 anal/oral sex partners in the past six months (P6M) reported their own and partners’ HIV status and PrEP use. After stratifying by respondents’ HIV status (positive/negative/unknown) and P6M PrEP use (yes/no), we compared observed seroconcordance to that expected by chance among P6M-partnerships with known-status. Within HIV negative-concordant recent partnerships, we compared observed concordance in PrEP use at last sex to chance. Concordance by chance is calculated under proportionate-mixing assumption, which means the distribution of partnerships by partners’ attributes equals that by respondents’ attributes as a result of partnership balancing. We used chi-squared tests for all comparisons. Results Of the 22,102 P6M-partnerships reported by 1881 respondents (17.0%, 74.5% and 8.5% HIV-positive, negative and unknown, respectively), 60.2% comprised partners’ of known-status. 64.3% of HIV-positive respondents’ partnerships were HIV-positive (vs chance 24.6%, p<0.001). HIV-negative or status-unknown respondents had higher proportions of HIV-negative partners (87.0% and 87.5%, respectively, vs chance 75.4%, p<0.001). HIV-negative respondents on PrEP had a higher proportion of HIV-positive partners than those not on PrEP (20.6% vs 8.4%; p<0.001). HIV-negative respondents on PrEP had a higher proportion of HIV-negative partners on PrEP (55.8% vs 34.7%); those not on PrEP had a higher proportion of HIV-negative partners not on PrEP (78.6% vs 65.3%), than chance (p<0.001). Conclusion Network-level serosorting and PrEP matching were evident after accounting for distribution of partnerships by chance. PrEP-mediated changes to mixing, such as less serosorting among MSM on PrEP, may indirectly influence the population-level HIV prevention impact of PrEP and should be included in the monitoring and evaluation of PrEP roll-out. Disclosure No significant relationships.
Source: Sexually Transmitted Infections
Institutions: St. Michael's Hospital, MAP Centre for Urban Health Solutions, Institut National de Santé Publique du Québec, University of Toronto, Toronto Metropolitan University, McGill University, University of Victoria, University of British Columbia, Johns Hopkins University, BC Centre for Excellence in HIV/AIDS
Language: English
Subfield: Infectious Diseases
Field: Medicine
Domain: Health Sciences
Open Access status: bronze
OpenAlex ID: W2966038500