WHO approves clinical trials on two new Ebola vaccines

WHO approved expert recommendations to add two new vaccine candidates to a clinical trial in the Democratic Republic of Congo. The trial already included Ervebo, which is approved for Ebola virus but not for the Bundibugyo virus causing the outbreak described here. This approval concerns testing, not final approval for public use.

The added candidates are ChAdOx1 BDBV and Moderna’s mRNA-1469. Oxford University developed ChAdOx1 BDBV with the Serum Institute of India. Moderna developed mRNA-1469. Both were created specifically for Bundibugyo virus, according to WHO chief Tedros Adhanom Ghebreyesus.

The DRC’s National Institute for Biomedical Research is leading the trial, with WHO and other partners supporting it. Testing could show whether either candidate is safe and effective against the virus driving this outbreak. Until then, WHO stresses early care, tracing, isolation, safe burials, and community trust.

Bundibugyo virus is a distinct type, or species, of Ebola virus that can cause Ebola disease. The outbreak described in the article involves Bundibugyo virus in the Democratic Republic of Congo. The article does not provide a detailed biological comparison between the two viruses, so this distinction is the key point it establishes.

Ervebo is already approved for Ebola virus, but Tedros Adhanom Ghebreyesus said it is not approved for Bundibugyo virus. That means approval for one virus does not automatically establish approval for another related virus. Vaccines are designed around the virus features the immune system must recognize.

The two proposed candidates, ChAdOx1 BDBV and mRNA-1469, were developed specifically for Bundibugyo virus. Their clinical trial will test whether they can safely protect people against the virus involved in this outbreak. The article does not state the candidates’ results yet.

Africa’s ongoing Ebola epidemic had reached 10,444 confirmed cases, according to the Africa Centres for Disease Control and Prevention. More than 5,300 people had died. The vast majority of those deaths occurred in the Democratic Republic of Congo, where the Bundibugyo virus outbreak was being fought.

A fatality rate of more than 50 percent means that over half of the confirmed cases had resulted in death in the figures reported. This makes the outbreak both large and exceptionally dangerous. The numbers also explain why researchers and health officials are seeking vaccines matched to the virus involved.

The scale creates urgent pressure for several responses at once. Vaccines could become an additional tool if they prove safe and effective. WHO also emphasized measures already known to save lives: early care, contact tracing, isolation, safe and dignified burials, and trusted engagement with communities.

An approved vaccine is not automatically approved for every related virus. The article states that Ervebo is approved for Ebola virus but not for Bundibugyo virus, which is ravaging the Democratic Republic of Congo. Because the outbreak involves a different virus type, researchers need candidates designed and tested for that specific threat.

The clinical trial began last month with Ervebo. WHO expert groups then recommended adding ChAdOx1 BDBV and Moderna’s mRNA-1469. Both candidates were developed specifically for Bundibugyo virus. Their inclusion allows researchers to assess options that match the virus identified in the outbreak.

This does not mean Ervebo is useless, or that either new candidate is already proven. It means their safety and effectiveness still need clinical testing. While that work continues, WHO says responses must also rely on early care, contact tracing, isolation, safe burials, and trusted community engagement.

If one candidate proves safe and effective, health officials could gain a vaccine specifically suited to the Bundibugyo virus outbreak. That would add another protective tool during an epidemic that had killed more than 5,300 people and recorded 10,444 confirmed cases. The article does not predict a specific outcome, so any benefit remains conditional.

The candidates are ChAdOx1 BDBV and Moderna’s mRNA-1469. Both were developed specifically for Bundibugyo virus. Clinical testing is the key mechanism for determining whether either vaccine works safely in people. The DRC’s National Institute for Biomedical Research is leading the trial, with WHO and partners backing it.

Even a successful vaccine would not replace other controls. Tedros said vaccines are powerful tools, but stressed early care, contact tracing, isolation, safe and dignified burials, and trusted engagement with communities. The strongest response would therefore combine vaccination with these proven measures.

The Democratic Republic of Congo’s National Institute for Biomedical Research is responsible for leading the clinical trial. This places the country’s biomedical research institution at the center of testing vaccines during the outbreak. The trial is backed by partners, including the World Health Organization.

WHO expert groups recommended adding the two candidates. WHO chief Tedros Adhanom Ghebreyesus announced the recommendation and explained why candidates targeting Bundibugyo virus were needed. International research partners contributed development expertise: Oxford University worked with the Serum Institute of India on ChAdOx1 BDBV, while Moderna developed mRNA-1469.

These roles divide the work across local leadership, global health coordination, and vaccine development. The article does not list every partner or describe each operational task. It does establish that the DRC leads the trial, WHO supports it, and research institutions and companies developed the candidates for testing.

In general, a vaccine trains the immune system by showing it a harmless form or selected feature of a virus. The body builds immune memory against that feature. Later, if the matching virus appears, the immune system can respond more quickly and strongly. The article does not explain this mechanism; this is established medical knowledge.

Matching matters because related viruses are not identical. A vaccine designed for one virus may not be authorized or reliably protective against another. The article gives a direct example: Ervebo is approved for Ebola virus, but not for Bundibugyo virus. The two new candidates were developed specifically for Bundibugyo virus.

That design issue is central to the clinical trial. Researchers must test whether the candidates safely produce useful protection against the virus causing this outbreak. Until results are available, WHO says vaccines remain complementary to early care, contact tracing, isolation, safe burials, and trusted community engagement.