No abstract

ObjectivesUse of illicit substances during sex (chemsex) may increase transmission of HIV and other STIs. Pre-exposure prophylaxis (PrEP) is highly effective at preventing HIV transmission, providing an important prevention tool for those who practise chemsex. However, it does not prevent acquisition of other STIs. We aim to examine the impact of chemsex on STI incidence among gay, bisexual and other men who have sex with men (gbMSM), and transgender women using PrEP in Montréal, Canada.MethodsWe linked baseline sociodemographic and behavioural data with follow-up STI testing from 2013 to 2020 among PrEP users in the l’Actuel PrEP Cohort (Canada). Focusing on the 24 months following PrEP initiation, we estimated the effect of chemsex reported at baseline on cumulative incidence of gonorrhoea and chlamydia using Kaplan-Meier curves and survival analyses. We investigated the role of polysubstance use and effect modification by sociodemographic factors.ResultsThere were 2086 clients (2079 cisgender gbMSM, 3 transgender gbMSM, 4 transgender women) who initiated PrEP, contributing 1477 years of follow-up. There were no incident HIV infections among clients on PrEP. Controlling for sociodemographic confounders, clients reporting chemsex at baseline had a 32% higher hazard of gonorrhoea/chlamydia diagnosis (adjusted HR=1.32; 95% CI: 1.10 to 1.57), equivalent to a risk increase of 8.9 percentage points (95% CI: 8.5 to 9.4) at 12 months. The effect was greater for clients who reported polysubstance use (adjusted HR=1.51; 95% CI: 1.21 to 1.89). The strength of the effect of chemsex on STI incidence varied by age, education and income.ConclusionAmong PrEP users, chemsex at baseline was linked to increased incidence of gonorrhoea and chlamydia. This effect was stronger for people reporting multiple chemsex substances. The high STI incidence among gbMSM who report chemsex highlights the importance of PrEP for this population and the need for integrated services that address the complexities of sexualised substance use.

Background:In Canada, all provinces implemented vaccine passports in 2021 to increase vaccine uptake and reduce transmission in non-essential indoor spaces. We evaluate the impact of vaccine passport policies on first-dose COVID-19 vaccination coverage by age, area-level income and proportion racialized.Methods:We performed interrupted time-series analyses using vaccine registry data linked to census information in Québec and Ontario (20.5 million people ≥12 years; unit of analysis: dissemination area). We fit negative binomial regressions to weekly first-dose vaccination, using a natural spline to capture pre-announcement trends, adjusting for baseline vaccination coverage (start: July 3rd; end: October 23rd Québec, November 13th Ontario). We obtain counterfactual vaccination rates and coverage, and estimated vaccine passports' impact on vaccination coverage (absolute) and new vaccinations (relative).Results:In both provinces, pre-announcement first-dose vaccination coverage was 82% (≥12 years). The announcement resulted in estimated increases in vaccination coverage of 0.9 percentage points (p.p.;95% CI: 0.4-1.2) in Québec and 0.7 p.p. (95% CI: 0.5-0.8) in Ontario. In relative terms, these increases correspond to 23% (95% CI: 10-36%) and 19% (95% CI: 15-22%) more vaccinations. The impact was larger among people aged 12-39 (1-2 p.p.). There was little variability in the absolute impact by area-level income or proportion racialized in either province.Conclusions:In the context of high baseline vaccine coverage across two provinces, the announcement of vaccine passports led to a small impact on first-dose coverage, with little impact on reducing economic and racial inequities in vaccine coverage. Findings suggest the need for other policies to further increase vaccination coverage among lower-income and more racialized neighbourhoods and communities.

Purpose: Longitudinal data on the experience and perpetration of intimate partner violence (IPV) among gay, bisexual, and other men who have sex with men (GBM) is limited. We estimated the prevalence of past six-month (P6M) physical and/or sexual IPV (hereafter IPV) experience and perpetration, identified their determinants, and assessed temporal trends, including the impact of the COVID-19 pandemic. Methods: We used data from the Engage Cohort Study (2017-2022) of GBM recruited using respondent-driven sampling in Montréal, Toronto, and Vancouver. Adjusted prevalence ratios (aPR) for determinants and self-reported P6M IPV were estimated using generalized estimating equations, accounting for attrition (inverse probability of censoring weights) and relevant covariates. Longitudinal trends of IPV were also assessed. Results: Between 2017-2022, 1,455 partnered GBM (median age 32 years, 82% gay, and 71% white) had at least one follow-up visit. Baseline proportions were 31% for lifetime IPV experience and 17% for lifetime perpetration. During follow-up, P6M IPV experience was more common (6%, 95%CI: 5-7%) than perpetration (4%, 95%CI: 3-5%). Factors associated with P6M IPV experience include prior IPV experience (aPR=2.79, 95%CI: 1.83-4.27), less education (aPR=2.08, 95%CI: 1.14-3.79), and substance use (injection aPR=5.68, 95%CI: 2.92-11.54, non-injection aPR=1.70, 95%CI: 1.05-2.76). Similar factors were associated with IPV perpetration. IPV was stable over time; periods of COVID-19 restrictions were not associated with IPV changes in this cohort. Conclusion: Prevalence of IPV was high among GBM. Determinants related to marginalization are associated with an increased risk of IPV. Interventions should address these determinants to reduce IPV and improve health.