Abstract
Background
Mpox denotes a viral zoonosis caused by the Orthopoxvirus monkeypox (MPXV), which is endemic in West and Central Africa. In spring 2022, notable outbreaks of MPXV clade IIb were recorded in several high-income countries, predominantly affecting men who have sex with men (MSM). At the peak of the outbreak, over 200 new mpox cases per week were reported in Berlin, which constitutes one of the largest MSM population in Europe. Within the same year, the outbreak significantly declined, and it is unclear which factors contributed to this rapid decrease.
Methods
To investigate the concomitant effects of sexual contact networks, transient contact reductions and the effect of infection- vs. vaccine-derived immunity on the 2022 mpox outbreak, we calibrated an agent-based model with epidemic, vaccination, contact- and behavioral data.
Results
Our results indicate that vaccination has a marginal effect on the epidemic decline. Rather, a combination of infection-induced immunity of high-contact individuals, as well as transient behavior changes reduce the number of susceptible individuals below the epidemic threshold. However, the 2022 mpox vaccination campaign, together with infection-derived immunity may contribute to herd-immunity in the Berlin MSM population against ongoing clade I mpox outbreaks. Demographic changes and immune waning may deteriorate this herd immunity over time.
Conclusions
These findings highlight that, in addition to vaccination, timely and clear communication of transmission routes may trigger spontaneous protective behavior within key populations; underscoring the importance of targeted sexual health education as a core component of outbreak response.
Plain language summary
Mpox is a virus disease that is transmitted through direct contact with infected individuals or contaminated materials. In 2022, major Mpox outbreaks occurred in several countries, especially among men who have sex with men (MSM). At its peak, Berlin (Germany) reported over 200 new cases per week, but saw a rapid decline of cases during summer 2022. We used mathematical simulations to explore how patterns of sexual contact, temporary changes in behavior, and immunity from infection or vaccination may have impacted the outbreak. We found that vaccination had a minor effect, while immunity from past infections and behavior changes played a major role in reducing infections. These insights show that clear communication about virus spread can encourage protective behaviors, highlighting the importance of targeted sexual health education in containing sexually transmitted infections.
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Data availability
The datasets generated during the current study, as well as all input parameters for the simulations, are available via GitHub at https://github.com/KleistLab/mPox/tree/main/resultsand https://github.com/KleistLab/mPox/tree/main/parameters, respectively, and via Zenodo at https://zenodo.org/records/1701230475. The results of the seroprevalence study28 are excluded and can be obtained directly from the study’s authors upon reasonable request. The source data for all manuscript figures is available in Supplementary Data 1.
Code availability
Codes were written in Python 3.11.6 and are available via GitHub at https://github.com/KleistLab/mPox/tree/mainand via Zenodo at https://zenodo.org/records/1701230475.
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Acknowledgements
Funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) under Germany’s Excellence Strategy - The Berlin Mathematics Research Center MATH+ (EXC-2046/1, project ID: 390685689). The authors would like to thank the HPC Service of FUB-IT, Freie Universität Berlin, for computing time74.
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N.G., U.M., and M.v.K. conceptualized the paper. D.S., J.M., A.N., and A.J.S. were involved in data curation and data provision. U.M. and M.v.K. supervised the project. N.G. and H.-Y.K. performed the analysis. N.G. wrote the first draft with help from U.M. and M.v.K. N.L., A.N., and A.J.S. provided inputs to improve the content. All authors critically reviewed the manuscript and contributed to the final draft.
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Gubela, N., Kim, Hy., Lunchenkov, N. et al. Behavior change and infection induced immunity led to the decline of the 2022 Mpox outbreak in Berlin. Commun Med (2026). https://doi.org/10.1038/s43856-025-01340-5
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DOI: https://doi.org/10.1038/s43856-025-01340-5


