Scientists at Oxford University are developing a new vaccine that could be ready for clinical trials within two to three months to help tackle the Ebola emergency.
The outbreak, centred on the Democratic Republic of Congo, has resulted in 750 suspected cases and 177 deaths.
The rare species of Ebola, known as Bundibugyo, for which there is no proven vaccine, kills around a third of those infected.
There are no guarantees the vaccine will prove effective and it will take animal research and trials on people to know if it will be.
But scientists say they are working urgently in case the outbreak spirals and their experimental vaccine is needed.
The risk from the current Ebola outbreak has now been upgraded from "high" to "very high" in the Democratic Republic of Congo, by the World Health Organization (WHO).
In the wider region the risk is also now considered to be high but it remains low internationally, it added.
This comes after the WHO declared a public health emergency of international concern on Sunday, when it stressed that the outbreak was not a pandemic.
Another separate experimental Bundibugyo vaccine is also in development, but it is expected to take six to nine months for any dose of that to be ready for testing.
The vaccine being developed by UK scientists uses the same technology the team developed during the Covid pandemic.
It is a highly adjustable technology - known as ChAdOx1 - that can be quickly tweaked so it works against different infections.
During the pandemic it was loaded with genetic code from the Covid-virus.
This time it has been prepared with genetic code from the Bundibugyo species of Ebola.
It uses a common cold virus that normally infects chimpanzees but has been genetically engineered to make it safe for people.
Researchers use this modified cold virus to carry and deliver important genetic material about the Bundibugyo Ebola virus to cells, instructing them to recognise and fight off the actual disease.
The vaccine does not cause an infection or Ebola symptoms, but trains the immune system to give protection.
The WHO said earlier this week that there was no animal data yet to support the effectiveness of this particular vaccine.
"It is possible that doses of that could be available for clinical trial in two to three months, but there is a lot of uncertainty," a spokesman added, saying it would depend on animal trials as to whether it could be considered "a promising candidate research vaccine" for Bundibugyo.
The BBC understands that animal testing is now under way in Oxford.
The Serum Institute of India is lined up to mass produce the Ebola vaccine once Oxford can supply medical-grade material.
Prof Lambe, the Calleva Head of Vaccine Immunology at the Oxford Vaccine Group, told BBC News: "Once we get starting material to them they can go fast and they can go big."
The WHO says the vaccine could be available for use in clinical trials in two to three months.
Lambe says speed is a priority: "People are worried about this outbreak, generally, you prepare for the worst case scenario - hopefully contact tracing and quarantine is all that's needed, but we can't take our foot off the gas."
This current Ebola outbreak is challenging because it is caused by a rare species of the virus.
There are six species of Ebola virus, but only three cause large outbreaks in people.
Bundibugyo has only caused two previous outbreaks - in Uganda in 2007 and DR Congo in 2012 - and has not been seen for over a decade.
There is an Ebola vaccine for the more common Zaire species of Ebola, but there is no proven vaccine for Bundibugyo.
Ebola vaccines would not be used en mass in the same way as during the Covid pandemic.
Instead, they are used in a technique called ring vaccination - where only the people most likely to get infected are immunised, including the close contacts of cases of Ebola as well as healthcare workers who are treating sick patients who can be very infectious.
The Oxford research team had already been working on similar vaccines for the Sudan species of Ebola virus and Marburg virus.
