Merck’s Ebola vaccine Ervebo is licensed to protect against a single species of the virus — but a new human study suggests it may also offer some protection against a different strain now fueling one of the largest Ebola outbreaks on record.
The findings, published in the New England Journal of Medicine, come as the Democratic Republic of Congo battles a Bundibugyo ebolavirus outbreak in its northeastern region. As of this week, health authorities had recorded roughly 2,500 confirmed cases and about 1,000 deaths — the third-largest such outbreak ever documented, and the fastest-growing to date.
What the data show
Ervebo is approved against the Zaire species of Ebola, not Bundibugyo. But the same northeastern region saw more than 300,000 people vaccinated with Ervebo during a 2018–2020 Zaire outbreak, giving researchers a population to study.
Among confirmed cases with a known vaccination history, the authors report that nine people who had previously received Ervebo all survived. In one striking observation, three of eight exposed healthcare workers who had been vaccinated survived, while five unvaccinated colleagues died. The researchers stress these are observational signals, not proof from a controlled trial.
“I believe we have now reached the point where this question should no longer be debated, it should be tested,” said Edouard Lhomme, the study’s first author and a professor at the University of Bordeaux.
Why it matters
With roughly 500,000 Ervebo doses in the international stockpile, a vaccine that could be deployed against more than one Ebola species would be a meaningful tool in an outbreak that is still expanding. But the authors are careful to frame their work as a case for formal testing — not a green light for off-label use. This article is for general information and is not medical advice.