Mpox’s Uneven Spread in East Africa Reveals the High Cost of Delayed and Limited Vaccination

A new study shows mpox is spreading unevenly across East Africa, with some countries facing rapid transmission that small interventions cannot control. It finds that sustained, high vaccination coverage, often above 80 percent is essential to stop outbreaks, with behavioral measures helping but not replacing vaccines .

Mpox, once regarded as a rare zoonotic disease confined largely to forested parts of Central and West Africa, has re-emerged as a far more complex public health threat. Since 2022, outbreaks across East Africa have shown that the virus is no longer spreading only from animals to humans but is increasingly transmitted between people. A new study by researchers from Ajayi Crowther University and the Federal University Oye-Ekiti in Nigeria, La Trobe University in Australia, Tshwane University of Technology in South Africa, and the Black in Mathematics Association brings clarity to this shift, using data and mathematical modelling to explain why some countries are hit harder than others, and what it will take to stop the virus.

Five countries, very different outbreaks

The study focuses on Burundi, Uganda, Rwanda, the Democratic Republic of Congo (DRC), and Kenya, countries linked by geography and population movement but experiencing mpox very differently. Burundi initially controlled its outbreak through early detection, quarantine, and vaccination, keeping deaths at zero. However, by 2024, cases surged sharply, spreading across much of the country and affecting many children and young adults. Uganda’s situation is more severe. With a history of mpox and exposure to a more dangerous viral strain, the country has struggled with repeated outbreaks and the highest fatality rates in the region. Rwanda presents a more hopeful picture, having acted quickly with contact tracing, isolation, and vaccination, which kept transmission and deaths relatively low. Kenya lies somewhere in the middle, with mostly urban outbreaks and moderate mortality. The DRC remains the epicenter, facing tens of thousands of suspected cases and high death tolls, driven by delayed diagnosis, limited healthcare access, and difficult logistics.

Measuring how fast mpox spreads

To compare these outbreaks, the researchers estimated the basic reproduction number, known as R₀. This number describes how many people one infected person is likely to infect if no one is immune. Uganda recorded the highest R₀, meaning the virus can spread rapidly if controls weaken. Burundi and Kenya showed moderate values, while Rwanda’s R₀ suggested a slower spread. The DRC’s R₀ appeared lower, but the authors warn this does not mean the country is safer, rather, long-standing transmission and delayed detection mean many infections may go unnoticed until outbreaks are well underway. These differences show why a single, uniform response across countries is unlikely to work.

Why vaccination levels really matter

The study goes beyond measuring spread and asks a crucial question: how much intervention is enough? By simulating vaccination and other control measures, the researchers found that in high-transmission settings, small vaccination campaigns are simply not sufficient. In places like Uganda, vaccination coverage may need to exceed about 80 percent, even if vaccines are not perfectly effective, to reliably stop outbreaks. In countries with more moderate transmission, lower coverage could work, but the margin for error is narrow. A small rise in transmissibility can suddenly demand much higher vaccination levels. The findings underline a simple but uncomfortable truth: partial efforts may slow mpox, but they will not stop it.

Can behavior change help?

Behavioral measures, such as increased condom use, do help reduce transmission, especially where sexual contact is a major driver of spread. The models show that better condom use flattens infection curves and reduces total cases. However, behavior change alone rarely brings transmission below the critical point needed to end an outbreak. Vaccination consistently proves to be the strongest tool, with behavior acting as an important backup rather than a replacement. The study also estimates how many people could ultimately be infected under different scenarios, information that is vital for planning hospital beds, staffing, and medical supplies.

A clear message for policymakers

The takeaway is clear and direct. Mpox control in East Africa requires sustained, high vaccination coverage tailored to local conditions. Short-term campaigns or low coverage may offer temporary relief but are unlikely to prevent future resurgences. Surveillance, public awareness, and regional cooperation remain essential, especially given cross-border movement, but vaccination must be the backbone of any strategy. While the authors note that real-world factors, such as uneven healthcare access and changing behavior, add uncertainty, their results provide rare clarity on the scale of response needed. In a region where health systems are already under strain, knowing “how much is enough” could make the difference between containment and crisis.