Vaccination strategies to achieve outbreak control for MPXV Clade I with a one-time mass campaign in sub-Saharan Africa: a scenario-based modelling study
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Background
Limited mpox vaccination coverage, declining cross-protection from historical smallpox vaccination campaigns, and persistent zoonotic reservoirs leave many sub-Saharan countries susceptible to mpox outbreaks. With millions of vaccine doses made available to the region since late 2024 and the absence of country-specific guidelines for allocation, estimating the country-specific impact of one-time mass vaccination strategies is necessary for ongoing outbreaks and other countries at future risk.
Methods and findings
We adapted a next generation matrix model to project disease transmission potential for 47 sub-Saharan countries from 2025 to 2050 under four transmission scenarios with different contributions of community vs sexual contacts. The model was informed by mpox datasets from Clade Ia and Ib outbreaks in the Democratic Republic of Congo (DRC), and incorporated country-specific demographics, contact patterns, and historical smallpox vaccination coverage. We then assessed strategies to reduce disease transmissibility by calculating country-specific minimum vaccine coverages and evaluating one-time, age-specific mass vaccination campaigns. At least 20 of the 47 countries are estimated to require vaccination in 2025, and 36 in 2050, to guard against potentially forthcoming national outbreaks. For 11 Clade I-affected countries, the minimum required coverage is estimated to range from 0%–4.8% to 14.5%–19.5% in 2025 with increasing sexual transmission, rising to 0%–10.8% and 22.6%–26.0% in 2050, respectively. The prioritised age group for vaccination shifts from 0–4 years to 20–29 years with additional sexual transmission. Note that all the projections were based on the best available evidence of Clade I transmission in the DRC as of December 2024.
Interpretation
With diminishing smallpox-vaccination-induced immunity, increasing disease transmissibility and potential for persistent outbreaks are expected for mpox, necessitating growing vaccine demand for outbreak containment. Given probable supply constraints, our findings could guide the ongoing and future mass vaccination efforts in sub-Saharan Africa by emphasising the prioritisation of high-risk groups, where allocation strategies are tailored to the evolving epidemiological landscape of each country.
