Five months into the Ebola outbreak in the Democratic Republic of Congo, there is still no approved vaccine against the rare Bundibugyo strain that has now caused more than 4,000 deaths. But candidates currently undergoing trials give reason to hope, according to Emanuele Capobianco of Gavi, the global vaccine alliance.

The DRC's worst-ever Ebola outbreak has now passed the 9,000-case mark, with the number of deaths topping 4,000 at the beginning of this month.

Among the many challenges is the lack of any approved vaccines or treatments for the Bundibugyo strain of Ebola that is behind the outbreak.

The first clinical trial of a potential vaccine is expected to begin by the end of October, World Health Organization experts said on Tuesday.

Ervebo, a vaccine already approved for use against the more common Zaire strain of Ebola, will undergo a full-scale human trial in the DRC to see if it offers any cross-protection against Bundibugyo.

Two vaccines specifically for Bundibugyo are also being developed, one by the University of Oxford and another by the US-based Moderna group. They are currently in the early stages of testing in smaller-scale clinical trials.

Capobianco, director of global health security at Gavi, told RFI they have the potential to save lives in this and future Ebola outbreaks. RFI: What can you tell us about the development of a potential Bundibugyo vaccine?

Emanuele Capobianco: There is currently no approved vaccine specifically for this virus. However, several candidates are in development, which offers reason for hope.

Two are leading the way: one from the University of Oxford – developed with partners including the Serum Institute of India – and the one from Moderna, which uses messenger RNA (mRNA) technology. They rely on different platforms, but both target the Bundibugyo virus.

We are expecting the results of their phase 1 trials later in October. They will provide data on their safety and their ability to stimulate the immune system.

If the results are positive, phase 2 and 3 trials may begin on larger populations. These will last several months and will make it possible to evaluate their efficacy. If all goes well, a rollout could take place in the first half of 2027.

At the onset of the outbreak, Gavi mobilised $50 million (€44 million) to support the response, including access to vaccines. We are investing ahead of final results so that doses can be made available as soon as their efficacy is proven and their use is authorised.

Violence against healthcare workers in DRC hampers Ebola response RFI: In the meantime, could the existing Ervebo vaccine help?

EC: Ervebo is approved for use against the Zaire strain of Ebola. It is safe and highly effective against this virus, but its protection against Bundibugyo has not been established.

The global stockpile contains approximately 500,000 doses of Ervebo. If it is demonstrated to be effective against Bundibugyo, we will therefore have a tool that could be deployed rapidly.

At the request of the Congolese government, 70,000 doses were released in August from the global stockpile funded by Gavi. A portion is being used for studies. Healthcare workers are also being vaccinated as part of a research protocol: they are protected against the Zaire strain, and monitoring them will make it possible to study whether this also provides protection against Bundibugyo. RFI: What can be done before the vaccines arrive?

Ebola outbreaks have previously been contained without vaccination or specific treatment, through infection prevention, surveillance and early care. This outbreak, too, could be contained before the arrival of new vaccines.

Because of the security situation, the system is unable to detect cases early on, so we don't have have a strong surveillance system. We can't detect where the patients are, or support them as fast as required.

Seventy percent of deaths occur in communities, before patients even arrive in health facilities. A huge effort is needed to encourage people to go to health centres. We also need for health centres to get closer to people to provide the kind of support that will result in patients surviving.

By intervening early, you can reduce the number of infections from a single case. So there's a lot of work that can be done in this area.

Ebola outbreak spreads in DRC as misinformation hampers response RFI: How can you convince people to get vaccinated, when the vaccine they got during a previous outbreak does not necessarily protect them against the current one?

First, a vaccine with proven safety and efficacy has to be available. Beyond that, healthcare workers are essential allies. They set an example and explain the benefits. Having well-informed, empathetic health professionals is a crucial first step.

Radio and television also have a role to play. However, direct, personal interaction is vital. It is important to engage with respected figures within communities – such as religious leaders, teachers and elders – who are not necessarily political figures.

These trusted individuals play a vital role in bridging what I call the final distance – the gap between the syringe and the arm. Even when the vaccine is available, administering it hinges on trust. And trust is hard to build, easy to lose.

RFI: These new vaccines may not be available until after this outbreak is over. Will the current research help regardless?

We are running a marathon. We have already covered several kilometres by nearing the end of the phase 1 trials. The results may prove useful for the current outbreak, but we must also look further ahead.

If we secure an effective vaccine against Bundibugyo, we will be able to build a global stockpile, just as Gavi did for the Zaire strain. We will then have doses available for future epidemics – not only in the DRC but in other countries too.