New Bundibugyo Ebola vaccine trials launch as DR Congo outbreak reaches record scale

The World Health Organization (WHO) said on 4 August 2026 that clinical trials of candidate vaccines and treatments targeting the Bundibugyo species of Ebola are advancing as the outbreak in the Democratic Republic of the Congo (DRC) continues to expand, according to a report from UN News.

As of 1 August, WHO data showed 3,748 confirmed cases, including 1,657 deaths and 708 recoveries. This marks the largest Ebola outbreak ever recorded in the DRC, surpassing the 2018–2020 epidemic, and is driven by the Bundibugyo virus for which no licensed vaccines or specific treatments exist, as detailed by WHO and Reuters. The outbreak, declared in mid-May 2026, is centred in Ituri province and has spread to five provinces and 49 health zones.

Vasee Moorthy, acting lead of WHO’s R&D Blueprint, told reporters in Geneva that trial protocols prepared before the outbreak allowed research to start more quickly than in previous Ebola responses. “If you compare this outbreak to previous Ebola outbreaks, we have been able to start trials more quickly,” he said, according to Reuters. Results from the trials are expected to take several months.

A Phase 1 trial of a Bundibugyo-specific vaccine candidate developed by the University of Oxford’s Oxford Vaccine Group, backed by the Coalition for Epidemic Preparedness Innovations (CEPI) and manufactured with the Serum Institute of India, entered human testing in the United Kingdom on 24 July. The ChAdOx1 BDBV candidate uses a modified common cold virus platform similar to the Oxford/AstraZeneca COVID-19 vaccine and is assessing safety and immune response in healthy adults, as reported by CEPI and UN News.

A second candidate, Moderna’s mRNA-1469 vaccine using the company’s mRNA technology, began its first human trial in Canada after Health Canada clearance. The early-stage study aims to enrol about 80 healthy adults across three sites to evaluate safety and immune response, with CEPI providing up to $50 million in support, according to Reuters. Moderna has indicated plans to make at least 500,000 doses available to low- and middle-income countries at access pricing if approved.

In parallel, a clinical trial of a potential post-exposure prophylaxis is underway in Ituri province. Led by the DRC’s National Institute for Biomedical Research with international partners including ALIMA and Médecins Sans Frontières, the EBO-PEP trial is evaluating whether a 10-day course of the oral antiviral obeldesivir can prevent disease onset in confirmed high-risk contacts. Over 25 participants had been enrolled by early August, with three testing sites open and a fourth planned, per UN News and Reuters. A separate WHO-sponsored treatment trial at three facilities in Ituri has enrolled more than 50 confirmed patients assigned to experimental options.

WHO is also reviewing new animal data on whether the licensed Ervebo vaccine, effective against the Zaire strain, might offer cross-protection against Bundibugyo. A technical advisory group met recently and was expected to issue recommendations shortly, according to Moorthy as reported by UN News.

The outbreak is occurring amid insecurity, population displacement and high mobility in eastern DRC, complicating response efforts. UN agencies including UNHCR, UNICEF, WFP and MONUSCO are supporting screening, diagnostics, community engagement, treatment centre security and aid, while the UN’s Central Emergency Response Fund is releasing up to $60 million for response and preparedness in the DRC and neighbouring countries, as noted by UN News. Uganda declared the end of its outbreak on 28 July after 42 days without new local transmission, though the risk of reintroduction remains.