The University of Oxford and the Serum Institute of India have begun the world’s first human trial of a vaccine against the Bundibugyo strain of Ebola, enrolling 50 healthy adults in a Phase I study to assess safety and immune responses. The candidate, ChAdOx1 BDBV, uses the same adenovirus-vector platform as the Oxford/AstraZeneca Covid-19 vaccine. The trial launches as the outbreak in the Democratic Republic of the Congo (DRC) reaches 1,926 confirmed cases and 702 deaths across five provinces, with the rare Bundibugyo virus—for which no approved vaccine or treatment exists—now detected in the major transport hub of Kisangani, over 500 km west of the epicentre in Ituri.

Containment efforts are being undermined by a strike of unpaid health workers at a treatment centre in Ituri province, where epidemiologists, drivers and gravediggers blocked access on Monday after weeks without salaries from the Congolese government. Contact tracing has improved to 78.3 percent but remains below the 90–95 percent target recommended by the World Health Organization. The outbreak was initially missed for weeks because diagnostic tests targeted more common Ebola strains, and its origin is still unknown. The International Rescue Committee warns that undetected transmission chains are likely, and the WHO estimates a 70 percent probability of cross-border spread into South Sudan, where weak surveillance and limited health infrastructure could delay detection.

Viewed from Washington, the risk prompted Health Secretary Robert F. Kennedy Jr. to sign an order placing US citizens in the DRC on a “do-not-board” list until they have spent 21 days in a third country. The move follows confirmation that a second American aid worker, employed by Samaritan’s Purse, tested positive for Bundibugyo virus and was evacuated to Frankfurt University Hospital; a previous US patient was treated at Berlin’s Charité hospital in May and has since recovered. German authorities said the US requested assistance because of the country’s expertise and the shorter flight time from the DRC. Uganda has reported 20 confirmed cases and two deaths, while India has enhanced screening at international airports.

In parallel, a separate study of two potential treatments—Gilead’s remdesivir and Mapp Biopharmaceutical’s experimental antibody MBP134—has begun enrolling patients at a single treatment centre in Ituri, though not the one affected by the strike. The WHO cautions that the trial may require up to 1,000 participants and several months to yield efficacy data. The Serum Institute of India has manufactured and stockpiled 620,000 doses of the vaccine candidate for potential future use. The next operational milestone is whether Congolese authorities can resolve the labour dispute before the strike spreads to other facilities, while the clinical milestone is the completion of Phase I safety data, which will determine if the vaccine can advance to larger trials.