You have probably heard of Ebola. Its lesser-known relative, Marburg, is just as deadly. For nearly 60 years, no vaccine has been approved to stop it.
That may finally be changing. In April 2026, IAVI, a nonprofit vaccine research group, began the first human trial of its single-dose Marburg vaccine candidate. About 112 healthy adults are enrolled at sites across the United States.
A separate program from the Sabin Vaccine Institute is already further along. Its vaccine candidate reached Phase 2 testing in April 2025, with volunteers in the US and two African countries.
Marburg has never had an approved vaccine. The World Health Organization puts the average case fatality rate at around 50 percent, with past outbreaks reaching as high as 88 percent.
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Containment, isolation and contact tracing have been the only tools since the virus was first identified in 1967, when it infected lab workers handling African green monkeys.
How the two trial vaccines work
The IAVI candidate, called IAVI C104, uses a platform known as rVSV. A weakened animal virus is engineered to carry a Marburg surface protein, so the immune system learns to recognize it.
The same base technology is used in a licensed Ebola vaccine, which gives researchers more confidence that the approach can work in people.
Each trial participant will get one injection, with four different dose levels being tested. Safety and immune response are being tracked for six months.
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In animal studies, a single dose gave 100 percent protection against a lethal Marburg challenge, according to IAVI.
The Sabin candidate uses a different approach. Its carrier is a weakened chimpanzee cold virus known as cAd3, which also delivers a Marburg surface protein.
The Phase 2 trial has enrolled 200 US volunteers aged 18 to 70. Sites include Florida, Texas, Alabama and Illinois, with parallel work in Kenya and Uganda.
Mark Feinberg, IAVI's president and CEO, said the trial "represents an important step toward generating the data needed for eventual regulatory approval."
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Why the push is happening now
Marburg outbreaks are getting more frequent. Ethiopia confirmed its first-ever outbreak in November 2025, with 9 deaths among 14 confirmed cases before the country declared it over in early 2026.
In June 2026, Uganda reported a Marburg case in a 1-year-old child, in a country already battling a large Ebola outbreak.
Rwanda's 2024 outbreak alone saw more than 1,700 frontline healthcare workers vaccinated in a trial-based response, using the Sabin candidate under emergency rules.
Earlier Marburg outbreaks since 2022 have hit Ghana and Tanzania as well. The pattern has pushed health agencies to pour money into vaccine development that moved slowly for decades.
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What a usable vaccine would still require
Even if both candidates clear every test, approval is years away. A Phase 1 trial, like IAVI's, is designed to check safety and immune response in a small group.
It does not test whether a vaccine actually prevents infection. Sabin's Phase 2 trial reaches a wider group but also falls short of a full efficacy answer.
Anyone infected with Marburg today still depends on supportive care alone. The WHO says treating specific symptoms and giving fluids can improve survival, but no antiviral drug is approved either.
Anyone who develops a sudden high fever after travel to an outbreak region should contact a doctor without delay.
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This article is made and published by Aksel Kryhlmand, who may have used AI in the preparation.