What you need to know:
- The first participant received the Ervebo vaccine, which is approved for protection against the Zaire strain of Ebola
The Democratic Republic of Congo (DRC) has launched a clinical trial to assess whether an existing Ebola vaccine can protect against the Bundibugyo strain, as the country battles an outbreak that has caused more than 9,700 cases and 4,600 deaths.
The trial, named Tumaini, meaning hope in Kiswahili, began on Friday, October 23, in Bunia, the capital of Ituri Province in north-eastern DRC, which remains the epicentre of the outbreak.
The first participant received the Ervebo vaccine, which is approved for protection against the Zaire strain of Ebola. However, its effectiveness against Bundibugyo remains unproven, making the trial an important step towards establishing whether it can provide protection against the strain responsible for the current outbreak.
According to the trial organisers, the DRC had recorded 9,552 cases and 4,602 deaths by October 21, making the outbreak the largest recorded of its kind involving the Bundibugyo virus.
There is currently no approved vaccine specifically targeting this strain, while the absence of proven vaccine protection presents an additional challenge for health authorities seeking to contain the outbreak.
The World Health Organisation (WHO) is supporting the DRC-led initiative, which aims to generate evidence on the safety, immune response and effectiveness of vaccine candidates against the virus.
WHO Director-General Tedros Adhanom Ghebreyesus announced the start of the trial, saying the research would help establish whether the vaccine candidates could protect people at risk of infection.
The trial will initially evaluate Ervebo to determine whether it offers cross-protection against Bundibugyo, despite being licensed for use against a different Ebola strain.
More vaccines to be assessed
Tumaini is designed as an adaptive clinical trial, allowing researchers to assess several vaccine candidates within a single research framework. This approach is intended to speed up the collection of evidence during the outbreak.
The study will use a ring-vaccination approach, which involves targeting people who have been in contact with confirmed Ebola patients and others considered at high risk of infection.
The trial is also expected to include pregnant women and children aged 12 and above, groups that are often excluded from clinical research, to help generate evidence on vaccine performance among these populations.
Two additional vaccine candidates specifically developed against the Bundibugyo virus are expected to join the trial after progressing through earlier stages of clinical research.
One is being developed by the University of Oxford in collaboration with the Serum Institute of India, while the other is being developed by US biotechnology company Moderna.
Both candidates have received funding from the Coalition for Epidemic Preparedness Innovations (CEPI) and are undergoing preliminary research to establish their safety and ability to trigger an immune response before joining the wider trial.
Their effectiveness against Bundibugyo will need to be established through further research.
Outbreak response
The outbreak was declared in May 2026 and has since expanded across several areas, placing pressure on health authorities to strengthen surveillance, identify infections and trace contacts.
The WHO has classified the situation as a public health emergency of international concern, reflecting the risk posed by the outbreak and the need for coordinated efforts to control its spread.
Bundibugyo is a distinct type of Ebola virus. The disease can spread through direct contact with the blood or other bodily fluids of an infected person, or with contaminated materials. Symptoms may initially include fever, fatigue, muscle pain and headaches before progressing to more severe illness.
The lack of an approved vaccine specifically against Bundibugyo means that researchers must establish whether existing or newly developed candidates can provide effective protection against the strain.
The Tumaini trial is expected to provide evidence that could guide decisions on the use of vaccines against Bundibugyo and help strengthen preparedness for future outbreaks.
However, researchers caution that the vaccines under investigation cannot yet be regarded as proven protection against the strain. Their safety and effectiveness must be established through the clinical trial process.