Ebola vaccine trial launches in DRC as outbreak becomes deadliest in the country's history

The Democratic Republic of Congo is fighting its largest-ever Ebola outbreak — and now it's trying an unconventional tool to slow it down. Health and frontline workers in eastern DRC have begun receiving doses of Ervebo, Merck's approved Ebola vaccine, in a compassionate-use program and a formal Phase 3 clinical trial. The catch: Ervebo was designed to fight the Zaire strain of Ebola, not Bundibugyo — the strain driving this outbreak. Early animal studies and anecdotal reports from the field suggest some cross-protection may exist, but the trial aims to find out for sure.

The WHO allocated 70,000 doses for DRC — 50,000 for frontline workers and 20,000 for the clinical trial — with Gavi committing $13 million to fund the effort. The IHR Emergency Committee is urging urgent, coordinated action, warning that without a rapid change in trajectory, the epidemic could have "profound national and regional consequences."

By the Numbers:

• 7,541 confirmed cases and 3,639 deaths recorded so far
• 48% overall case-fatality rate — rising even higher in some areas
• Children account for 1 in 4 cases and 1 in 3 deaths; fatality rate among kids under 5 is 60%
• Ervebo is 84% effective against Ebola Zaire; efficacy against Bundibugyo is unknown
• The outbreak is growing approximately 7x faster than the 2014–2016 West Africa outbreak at the same time point

Why it matters: This trial could redefine how the world responds to future Ebola outbreaks. If Ervebo proves effective against Bundibugyo, it would give health officials a licensed, stockpiled tool to deploy against a strain that currently has no approved vaccine or treatment — a potential game-changer for outbreak response in the region and beyond.