Epidemiological characteristics and vaccination impact scenario modelling of concurrent Clade I mpox outbreaks in the Democratic Republic of the Congo and Burundi

Abstract In 2024, mpox cases surged in the Democratic Republic of the Congo (DRC) with cross-border spread to Burundi. We developed a transmission-dynamic model calibrated against surveillance data to understand drivers in enzootic (Clade Ia) and non-enzootic (Clade Ib) areas, and the potential impact of vaccination. In non-enzootic areas we estimated that 58-84% of transmission occurred within sexual networks. MVA-BN vaccination of sex workers could have averted 91% (95% CrI 81%–98%) of infections in Sud Kivu (DRC) but only 35% (95% CrI 26%–47%) in Bujumbura (Burundi), due to later outbreak detection. In historically enzootic Equateur (DRC), ongoing zoonotic spillover best explained sustained incidence. There, pledged Lc18m8 vaccines could have averted 42% (95% CrI 40%–46%) of infections; prioritising children improved impact. Across all settings, doubling vaccine coverage by using a single dose of MVA-BN outperformed two-dose strategies. Timely detection and tailored vaccination strategies are critical to reducing mpox burden.