The recommendations come amid concerns over the spread of Ebola Virus Disease caused by the Bundibugyo virus, a less common but potentially deadly strain currently affecting parts of Uganda and the Democratic Republic of the Congo (DRC).
To accelerate response efforts, WHO convened leading scientists, vaccine experts and advisory groups to evaluate available medical countermeasures and determine which candidates should be prioritised for research and deployment.
Following extensive consultations, the experts agreed that all identified vaccines and therapeutics should be used strictly within carefully designed clinical trials. According to WHO, this approach is necessary to generate reliable scientific evidence while ensuring that research is conducted safely, ethically and effectively.
Single-Dose Vaccine Emerges as Leading Candidate
Among the vaccine candidates reviewed, experts identified the single-dose rVSV Bundibugyo vaccine, currently being developed by the International AIDS Vaccine Initiative (IAVI), as the most promising option.
The vaccine is designed specifically to target the Bundibugyo strain of the Ebola virus and could potentially provide effective protection against infection if ongoing development efforts prove successful.
However, WHO noted that the vaccine is still several months away from clinical evaluation. Current projections suggest that it may take between seven and nine months before the candidate is ready to undergo efficacy testing in human trials.
The organisation emphasised that although the vaccine shows promise, additional development work remains necessary before its effectiveness can be properly assessed during outbreak settings.
Second Vaccine Candidate Could Be Available Sooner
Experts also reviewed another vaccine candidate, ChAdOx1 Bundibugyo, being jointly developed by the University of Oxford and the Serum Institute of India.
Unlike the rVSV candidate, WHO indicated that the ChAdOx1 vaccine could potentially become available for efficacy studies within two to three months, making it a potentially valuable option for ongoing outbreak response efforts.
Despite the accelerated timeline, researchers say further animal studies will be required before the vaccine can be fully prioritised for large-scale clinical evaluation.
Scientists noted that different vaccination approaches may be considered depending on the target population.
According to the experts, a single-dose regimen could be suitable for people who have come into contact with confirmed Ebola patients, while a two-dose schedule may be more appropriate for healthcare workers, emergency responders and other frontline personnel at elevated risk of exposure.
WHO Identifies Three Priority Treatments
Alongside vaccine development, WHO experts also examined potential treatments for individuals already infected with the Bundibugyo virus.
After reviewing available evidence, the advisory groups recommended prioritising three candidate therapeutics for clinical trials.
The shortlisted treatments include the monoclonal antibodies MBP134 and Maftivimab, as well as the antiviral medication Remdesivir.
Researchers also recommended evaluating a combination treatment strategy involving one of the monoclonal antibodies together with Remdesivir, a move aimed at determining whether combined therapies could improve patient outcomes.
Monoclonal antibodies work by helping the immune system identify and neutralise harmful viruses, while antiviral medications seek to limit the virus's ability to replicate inside the body.
Oral Drug Considered for Preventing Infection After Exposure
For individuals who may have been exposed to Ebola through contact with infected persons, experts identified the antiviral drug Obeldesivir as a priority candidate for post-exposure prevention research.
The proposed study would involve administering oral tablets of Obeldesivir to people who have had close contact with confirmed or probable Ebola cases to determine whether the medication can stop the disease from developing.
However, WHO cautioned that the success of such an intervention would depend heavily on rapid and effective contact tracing systems.
Public health experts acknowledge that identifying and monitoring contacts remains one of the most challenging aspects of Ebola outbreak control, particularly in remote or conflict-affected areas of the Democratic Republic of the Congo.
Licensed Ebola Vaccine Not Yet Approved for Bundibugyo Strain
The experts also considered whether Ervebo, currently the world's only licensed Ebola vaccine, could play a role in controlling the outbreak.
While Ervebo has proven highly effective against the Zaire strain of Ebola—the most common Ebola virus responsible for outbreaks across Africa—WHO noted that the vaccine is not licensed for protection against Bundibugyo virus disease.
The organisation explained that available evidence regarding cross-protection against other Ebola species remains limited and inconclusive.
As a result, WHO advised that Ervebo should only be used within carefully monitored research settings where scientists can accurately assess its effectiveness against the Bundibugyo strain.
Accelerating Research During Public Health Emergencies
The latest recommendations were issued through WHO's Research and Development (R&D) Blueprint programme, a global initiative designed to speed up scientific research during epidemic outbreaks.
The programme enables rapid coordination among governments, researchers, pharmaceutical developers and public health agencies to fast-track the development of diagnostics, vaccines and treatments during health emergencies.
WHO said it is working closely with authorities in Uganda and the Democratic Republic of the Congo to facilitate clinical studies and evaluate the identified medical products as quickly as possible.
As both countries continue efforts to contain the outbreak, health experts say the success of ongoing research could prove critical in strengthening global preparedness against future Ebola emergencies and preventing wider public health crises.