Several non-profit organizations announced Monday they are ramping up efforts to rapidly develop a vaccine for the rare strain of Ebola driving a deadly outbreak in the Democratic Republic of Congo.
Nearly 250 people are suspected to have died and more than 1,100 infected with the strain in the DRC and neighboring Uganda, though the true spread of the virus is feared to be much wider.
While it marks the 17th Ebola outbreak in the DRC, it is just the third caused by the Bundibugyo strain, for which there are no approved vaccines or treatments.
The escalating nature of the outbreak has sparked a race to find a vaccine that can be quickly developed, manufactured then tested in humans during clinical trials in the affected region.
The World Health Organization said on Saturday that its experts had determined "the most promising candidate vaccine" was a single-dose shot using the rVSV platform.
The only licensed Ebola vaccine, which targets the more common Zaire strain, uses the same platform.
The non-profit International AIDS Vaccine Initiative (IAVI) announced Monday it had reached a deal with the University of Texas Medical Branch to develop the rVSV candidate.
The university's Thomas Geisbert led work on both the Bundibugyo candidate and the licensed Zaire jab.
Geisbert told AFP last month that 2013 research demonstrated his jab provided very strong protection against Bundibugyo in monkeys.
However the vaccine "just sat there" for more than a decade because of a lack of interest, in particular from pharmaceutical firms, the virologist added.
The WHO estimated it would take seven to nine months before the rVSV vaccine is ready to be tested in humans.
- 'Fast-track' -
Also on Monday, the Coalition for Epidemic Preparedness Innovations (CEPI) announced funding to "fast-track" development of three Bundibugyo vaccine candidates, including $3.2 million towards the rVSV jab.
WHO chief Tedros Adhanom Ghebreyesus, who visited the epicenter of the outbreak in the DRC on the weekend, said in a statement the funding was "an important step forward".
Another vaccine candidate receiving CEPI funding was developed on the University of Oxford's ChAdOx1 platform, which also underpinned AstraZeneca's Covid vaccine.
This viral vector jab -- which will be manufactured by the huge Serum Institute of India -- could become available for clinical trials within two to three months, the WHO said.
CEPI also said it had committed $50 million to a vaccine candidate being developed by US pharma giant Moderna which uses the mRNA technology pioneered in its Covid vaccine.
In a preprint paper published online last week, researchers at France's INSERM institute called for trials to see if the licensed Zaire vaccine could also help fight Bundibugyo.
- $50 million pledge -
Also on Monday, the Gavi vaccine alliance announced it would make up to $50 million available for Bundibugyo vaccine efforts.
"We need to act now to ensure that, once one or more vaccine candidates are ready, manufacturers are in a position to start producing doses at scale," Gavi CEO Sania Nishtar said in a statement.
IAVI president Mark Feinberg told a press conference on Monday that Gavi's new commitment could fund the production of roughly 500,000 doses.
It also provided a "signal to manufacturers they can make this investment and not carry excessive risk," he added.
Even once doses for a trial are ready, there will be challenges in deploying them in a vast, remote area of the DRC that is already suffering crises including hunger, malaria and conflict.
Gaining the trust of communities where vaccines will be trialed will be crucial, the WHO emphasized.
And once a trial is finally carried out, there is no guarantee it will demonstrate the vaccine works.
"We have reasons to believe that we can generate effective vaccines, but we don't want to downplay at all that we have to treat them as investigational products," CEPI CEO Richard Hatchett said last week.
There are also several efforts to quickly trial several Bundibugyo treatments, including antivirals called remdesivir and obeldesivir, and the monoclonal antibody MBP134.
