Optimizing vaccination strategies for mpox control in endemic areas: Modeling insights from the Democratic Republic of Congo

• Ring vaccination reduces outbreak cluster sizes even with 25–50% case reporting. • Sexual transmission pathways decrease the effectiveness of ring vaccination. • Strong surveillance and early detection improve vaccination impact, even with delays. The global mpox outbreak of 2022, caused by the Clade IIb strain of monkeypox virus, underscored the potential of this virus to pose a significant public health threat on a global scale. The Democratic Republic of Congo is currently facing multiple outbreaks associated with Clade I. Effectively controlling localized community transmission within endemic areas through vaccination can reduce the likelihood of broader regional or even global outbreaks. Large-scale community vaccination in DRC is challenged by limited resources, including vaccine availability during early outbreaks in remote areas, whereas limited surveillance, contact tracing, and accessibility to remote locations can reduce the effectiveness of targeted ring vaccination. Furthermore, recent outbreaks in DRC have been driven by both sexual and non-sexual close contact transmissions. Here, we used an agent-based model with stochastic transmission within and between households to assess the effectiveness of ring vaccination for controlling localized community transmission in the presence of incomplete case reporting and delay in vaccination. We consider both nonsexual close contact and sexual transmission. We found that ring vaccination, even with 25-50% reporting, is effective in reducing outbreak cluster sizes and the likelihood of large cluster sizes (>5 cases), particularly when implemented shortly after detection of initial cases. The effectiveness of ring vaccination reduces with the inclusion of sexual transmission. We show that outbreak size and the likelihood of large clusters are reduced when responding to every reported infection, even with 2-3 weeks of delay. Settings with strong surveillance systems characterized by high levels of reporting will have earlier case detection, enabling earlier response and improving the effectiveness of ring vaccination.