Impact of interventions on mpox transmission during the 2022 outbreak in Canada: a mathematical modeling study of three different cities.

Objectives: The global mpox (clade II) outbreak of 2022 primarily affected gay, bisexual, and other men who have sex with men (GBM) and was met with swift community and public health responses. We aimed to estimate the relative impact of changes in sexual behaviours, contact tracing/isolation, and first-dose vaccination on transmission in Canadian cities.
Methods: We estimated changes in sexual behaviours during the outbreak using 2022 data from the Engage Cohort Study which recruited self-identified GBM in Montréal, Toronto, and Vancouver (n=1,445). We developed a transmission dynamic model to estimate the averted fraction of new infections attributable to the three interventions in each city.
Results: The empirical estimates of sexual behaviours changes were imprecise: 20% (RR=0.80; 95% credible intervals [95%CrI]: 0.47-1.36) fewer sexual partners in the past 6 months among those reporting ≤7 partners and 33% (RR=0.67; 95%CrI: 0.31-1.43) fewer among those with >7 partners. The three interventions combined averted 46%-58% of cases. Reductions in sexual partners, contact tracing/isolation prevented approximately 12% and 14% of cases, respectively. Vaccination's effect varied across cities by start date and coverage, with 21%-39% mpox infections prevented.
Conclusions: Reduction in sexual activity, contact tracing/isolation, and vaccination all contributed to accelerating epidemic control. Early vaccination had the largest impact.
Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Joseph Cox reports research grants from Gilead Sciences Canada and ViiV Healthcare, all outside of the submitted work. Mathieu Maheu-Giroux reports contractual arrangements from the World Health Organization, the Joint United Nations Programme on HIV/AIDS (UNAIDS), and the Public Health Agency of Canada, all outside of the submitted work. Trevor A. Hart reports educational grants from being an Advisory Committee member for the Canadian Institutes of Health Research (CIHR)’s Institute of Infection and Immunity and funds for community engagement events from ViiV Healthcare and Gilead Sciences Canada, all outside of the submitted work. Darrell H.S. Tan's institution has received investigator-initiated grants from Abbvie and Gilead, and support for participation in clinical trials sponsored by Glaxo Smith Kline, all outside of the submitted work. All other authors report no conflict of interest.
(Copyright © 2025. Published by Elsevier Ltd.)