A Trial Called Hope Launches to Fight the Deadliest Ebola Outbreak in Congo's History

A Crisis Without a Cure

The Tumaini trial begins as the Democratic Republic of Congo faces the largest recorded Bundibugyo virus outbreak ever documented. The outbreak was officially declared on May 15, 2026, and was subsequently designated a Public Health Emergency of International Concern by the WHO. With more than 9,700 cases and over 4,600 deaths, the scale of this epidemic is staggering — and until now, health workers have been fighting it without a single approved weapon specifically designed to stop it.

The trial comes amid deep concerns over the absence of an approved vaccine specifically targeting the Bundibugyo strain of Ebola. Although Ervebo is approved for preventing Ebola virus disease caused by the Zaire strain, its effectiveness against the Bundibugyo strain has not been established in humans. That gap in science is exactly what this trial is racing to close.

What the Tumaini Trial Is and How It Works

The trial, known as Tumaini — meaning "hope" in Swahili — will investigate whether existing and experimental vaccines can protect against the Bundibugyo strain of Ebola responsible for the current epidemic. It began on Friday, October 23, with the first participants receiving the Ervebo vaccine in Bunia, the capital of Ituri Province in northeastern DR Congo, which is at the center of the outbreak.

The trial uses an adaptive platform design, allowing multiple vaccine candidates to be evaluated within a single study through a ring vaccination approach targeting contacts of confirmed cases. Each person within a ring will be randomized. For now, half will receive the Ervebo vaccine on Day 1 and a typhoid vaccine four weeks later; for the other half, the sequence is reversed. This design mirrors a strategy that proved effective in a landmark 2015 Ebola trial conducted in Guinea.

The trial will include pregnant women and children aged 12 years and older, generating evidence for populations that are often excluded from clinical trials. That inclusion is significant — these groups are often among the most vulnerable during outbreaks, yet they are routinely left out of the data that shapes global health policy.

Two More Vaccines Waiting in the Wings

One candidate in the pipeline is a ChAdOx1 adenoviral vector vaccine being developed by the University of Oxford; the other, by the US-based Moderna group, uses mRNA technology. Both have received funding from the Coalition for Epidemic Preparedness Innovations and are expected to enter the trial "shortly," CEPI said in a statement.

The Oxford vaccine contains a surface protein of Bundibugyo stitched into a chimpanzee adenovirus — a platform the university has used successfully in other vaccine programs. The involvement of Moderna brings mRNA technology into the fight against Ebola for the first time at this scale, reflecting how rapidly that platform has matured since its COVID-19 debut.

The trial is coordinated by Congo's National Institute for Biomedical Research with the University of Antwerp and support from WHO, the Congolese Ministry of Health, CEPI, and other partners. WHO Director-General Tedros Adhanom Ghebreyesus framed it simply: "This trial will help us understand whether any of the vaccine candidates designed for Bundibugyo virus work."

Why This Moment Matters Beyond Congo

CEPI said Tumaini "will work closely with affected communities, health authorities and outbreak response partners to generate robust evidence on vaccine performance that could contribute to curtailing the epidemic, saving lives, and strengthening preparedness for future Bundibugyo outbreaks." That last phrase carries enormous weight. A proven vaccine against Bundibugyo wouldn't just help contain the current crisis — it would give the world a tool it has never had before.

The Tumaini trial represents something rare in global health: a large-scale clinical study launched in the middle of an active, devastating outbreak. The trial "will generate urgently needed data on the efficacy of Ervebo against Bundibugyo virus disease, and will help formulate the policy decisions we need," said Anthony Scott, chair of WHO's Strategic Advisory Group of Experts on Immunisation. With the Oxford and Moderna candidates expected to join the platform in the coming weeks, the pace of this science — and the lives depending on it — will only intensify.