Ebola vaccine research faces hurdles in DRC outbreak

Ebola has been known for decades, but there is still no licensed vaccine against the Bundibugyo strain of the virus causing the current outbreak in the Democratic Republic of Congo (DRC). The virus was identified in 2007 during an outbreak in Bundibugyo, Uganda, and another outbreak occurred in the DRC in 2012.

Torsten Feldt, a doctor of tropical medicine at Düsseldorf's University Hospital, said: "We had come across the Bundibugyo virus in two previous outbreaks: 2007 in Uganda and 2012 in DR Congo. So we had enough time to develop vaccines and therapeutic options. But we didn't make use of this opportunity, meaning crucial time was lost during the current outbreak."

Leonie Mayer from the German Center for Infection Research (DZIF) and the Institute for Infection Research and Vaccine Development at the University Medical Center in Hamburg-Eppendorf said: "They could of course have developed a vaccine and run pre-clinical trials before." She stressed that effectiveness can only be assessed and confirmed during an actual outbreak.

Mayer is the lead author of a recently published study that examined whether Ervebo, an Ebola vaccine that has already been licensed, can be used against other types of Ebola as well. The study found cross-reactive T-cell responses against Bundibugyo, and also, to a lesser extent, against the Sudan virus. Mayer said: "We now know that the immune cells can most likely also recognize the Bundibugyo virus." She also said: "Our data does not enable us to answer the question of whether this immune response actually provides protection, or if it results in a milder progression of the disease."

The existing vaccine, Ervebo, was developed and licensed for use against the Zaire variant. There is still no approved protection against the Bundibugyo or Sudan variants.

The DRC has had more than 10,000 cases of Bundibugyo since May. Recently, it has also been reported in Kenya and Nigeria.

The so-called Tumaini study, which is testing different vaccine candidates, has now been launched in the DRC. These include Ervebo and a Moderna mRNA vaccine. The study aims to provide the first reliable data about their efficacy against the Bundibugyo virus. Experts estimate that, realistically, it will be several months before any such vaccine is available for widespread use; perhaps not until mid-2027.

Christof Geldmacher, a co-author of the DZIF study, said: "Ideally, we will develop cross-reactive pan-Ebola vaccines."

This article has been translated from German.

Sources

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