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

Fanyu Xiu; Carla Doyle; Jorge Luis Flores Anato; Jesse Knight; Linwei Wang; Joseph Cox; Daniel Grace; Trevor A Hart; Terri Zhang; Shayna Skakoon-Sparling; Milada Dvorakova; Rita Shahin; Herveen Sachdeva; Nathan Lachowsky; Hind Sbihi; Darrell H S Tan; Michael A Irvine; Sharmistha Mishra; Mathieu Maheu-Giroux

doi:10.1016/j.ijid.2025.107792

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

Int J Infect Dis. 2025 Jan 21:107792. doi: 10.1016/j.ijid.2025.107792. Online ahead of print.

Authors

Fanyu Xiu¹, Carla Doyle¹, Jorge Luis Flores Anato¹, Jesse Knight², Linwei Wang³, Joseph Cox⁴, Daniel Grace⁵, Trevor A Hart⁶, Terri Zhang⁷, Shayna Skakoon-Sparling⁸, Milada Dvorakova⁹, Rita Shahin¹⁰, Herveen Sachdeva¹⁰, Nathan Lachowsky¹¹, Hind Sbihi¹², Darrell H S Tan¹³, Michael A Irvine¹⁴, Sharmistha Mishra¹⁵, Mathieu Maheu-Giroux¹⁶

Affiliations

¹ Department of Epidemiology and Biostatistics, McGill University, Montréal, QC, Canada.
² MAP Centre for Urban Health Solutions, Unity Health Toronto, ON, Canada; Institute of Medical Sciences, University of Toronto, Toronto, ON, Canada.
³ MAP Centre for Urban Health Solutions, Unity Health Toronto, ON, Canada.
⁴ Department of Epidemiology and Biostatistics, McGill University, Montréal, QC, Canada; Research Institute of the McGill University Health Centre, Montréal, QC, Canada.
⁵ Dalla Lana School of Public Health, University of Toronto, Toronto, ON, Canada.
⁶ Dalla Lana School of Public Health, University of Toronto, Toronto, ON, Canada; Department of Psychology, Toronto Metropolitan University, Toronto, ON, Canada.
⁷ Department of Psychology, Toronto Metropolitan University, Toronto, ON, Canada.
⁸ Department of Psychology, Toronto Metropolitan University, Toronto, ON, Canada; Department of Psychology, University of Guelph, Guelph, ON, Canada.
⁹ Research Institute of the McGill University Health Centre, Montréal, QC, Canada.
¹⁰ Dalla Lana School of Public Health, University of Toronto, Toronto, ON, Canada; Toronto Public Health, ON, Canada.
¹¹ School of Public Health and Social Policy, University of Victoria, Victoria, BC, Canada.
¹² Data and Analytic Services, British Columbia Centre for Disease Control, Vancouver, BC, Canada; School of Population and Public Health, University of British Columbia, Vancouver, BC, Canada.
¹³ Institute of Medical Sciences, University of Toronto, Toronto, ON, Canada; Research Institute of the McGill University Health Centre, Montréal, QC, Canada; Department of Medicine, St. Michael's Hospital, University of Toronto, Toronto, ON, Canada.
¹⁴ Data and Analytic Services, British Columbia Centre for Disease Control, Vancouver, BC, Canada; Faculty of Health Sciences, Simon Fraser University, Burnaby, BC, Canada; Department of Statistics, University of British Columbia, Vancouver, BC, Canada.
¹⁵ MAP Centre for Urban Health Solutions, Unity Health Toronto, ON, Canada; Institute of Medical Sciences, University of Toronto, Toronto, ON, Canada; Dalla Lana School of Public Health, University of Toronto, Toronto, ON, Canada; Department of Medicine, St. Michael's Hospital, University of Toronto, Toronto, ON, Canada.
¹⁶ Department of Epidemiology and Biostatistics, McGill University, Montréal, QC, Canada. Electronic address: mathieu.maheu-giroux@mcgill.ca.

PMID: 39848438
DOI: 10.1016/j.ijid.2025.107792

Abstract

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.

Keywords: MVA-BN; Modified vaccinia Ankara; behavioural change; contact tracing; mathematical model; men who have sex with men; monkeypox; mpox; vaccination.