Temporary Adaptations to Sexual Behaviour During the Mpox Outbreak in 23 Countries in Europe and the Americas: Findings from a Retrospective Cross-sectional Online Survey

Background: After rapid epidemic growth between May and August, 2022, new mpox diagnoses declined in Europe and the Americas, with low-level transmission continuing thereafter. Characterising the extent of behavioural adaptation, mpox vaccination, and mpox prevalence across these regions could improve our understanding of the transmission dynamics of the virus. We aimed to characterise the presence and duration of adaptations to sexual behaviour related to the emergence of mpox during the first year of the outbreak among affected communities in Europe and the Americas.

Methods: This retrospective, cross-sectional online survey was conducted in 23 countries in Europe and the Americas between May 19 and May 31, 2023. The survey was advertised via four geospatial dating apps used by affected communities. Eligible participants were aged 18 years or older and identified as a gay man, a bisexual man, a man who has sex with men, as transgender, or as non-binary. We described and regionally compared the mpox prevalence, mpox vaccination rates (one dose or two doses of modified vaccinia virus Bavarian Nordic), and the extent and duration of behavioural adaptation during the outbreak. For these behavioural outcomes, we used regression analyses to estimate crude prevalence ratios (PRs) and adjusted prevalence ratios (aPRs) with 95% CIs.

Findings: Of 17 428 individuals who completed the survey, 16 875 (96·8%) met the eligibility criteria and were included in the study. 1086 (6·4%) participants reported having mpox during the outbreak. Vaccination with at least one dose was reported by 4987 (29·6%) participants; 3502 (20·8%) reported two doses. Vaccination rates in Latin America and eastern Europe and the western Balkans were significantly lower than in western Europe and northern America (p<0·0001). Adaptations to sexual behaviour were reported by 8583 (50·9%) of 16 875 participants and across all regions; 3045 (35·5%) of these 8583 participants said they continued adapting their sexual behaviour until May, 2023. Participants who reported concerns about mpox (9884 [58·6%] of 16 875) were more likely to adapt their behaviour than those who did not report concerns (PR 2·43 [95% CI 2·34-2·53]). In adjusted regression models, participants who reported vaccination (aPR 0·25 [95% CI 0·21-0·28] for two doses and 0·43 [0·37-0·51] for one dose) or having had mpox (0·37 [0·30-0·44]) were less likely to continue adaptations than those who did not. Participants in Latin America or northern America were significantly more likely to adapt their sexual behaviour and to continue with adaptations than those in western Europe.

Interpretation: Adaptations to sexual behaviour due to mpox were widespread, dynamic, and responded to evolving individual risk perceptions. We propose that the decline in mpox transmission seen at the end of 2022 resulted primarily from a combination of behavioural adaptation and naturally acquired immunity. As mpox vaccination is an important preventive measure, stark vaccine inequity highlights the need to increase access to mpox vaccines.

Funding: WHO Contingency Fund for Emergencies.