An Ebola vaccine developed in just eight weeks has been cleared for UK human trials, with the first doses due to be given within weeks.
The Medicines and Healthcare products Regulatory Agency (MHRA) has approved the experimental jab for testing in healthy adults.
It is the first of four vaccines being developed against the Bundibugyo species of Ebola to reach clinical trials.
Scientists at the University of Oxford began developing the jab after a public health emergency was declared on 17 May.
The phase one trial will recruit 50 healthy adults aged between 18 and 55. Phase one studies are early tests used mainly to assess safety and the immune system’s response.
The first UK participants are expected to receive doses within weeks. Researchers are also working with partners in Uganda to prepare for trials in Africa.
Dr Katrina Pollock, chief investigator of the trial, said: “We’re doing phase one (early stage) trials of new vaccines all of the time, precisely to be ready for exactly this kind of outbreak.”
The outbreak, centred on the Democratic Republic of the Congo, has killed 625 people, with 1,792 laboratory-confirmed cases reported.
It is caused by the Bundibugyo species of Ebola, which has caused two previous outbreaks.
Scientists have identified six species of Ebola. Although they are related, differences between them mean separate vaccines and treatments are needed.
There are currently no approved drugs or vaccines for the Bundibugyo species.
The outbreak remains uncontrolled and is taking place in a conflict zone where populations are highly mobile, increasing the need for a vaccine to help prevent the disease spreading.
Volunteers will be monitored for a year, although researchers expect to learn sooner whether the vaccine produces the intended immune response or causes unexpected side effects.
The jab uses the same technology as the Oxford/AstraZeneca Covid vaccine.
It is made using a common cold virus that infects chimpanzees and has been genetically modified to make it safe.
The harmless virus works as a carrier, known as a viral vector, delivering a small piece of genetic material from the Bundibugyo Ebola virus into the body.
The vaccine does not cause an infection, but the genetic material causes the body to produce a single Ebola protein.
This is enough to help the immune system recognise the virus and prepare a response.
The aim is to give the body a head start if a vaccinated person is later exposed to the real virus.
The experimental jab has been developed and tested in mice and macaque monkeys and is being manufactured to clinical standards by the Serum Institute of India.
The institute has manufactured and stockpiled about 620,000 doses.
The UK regulator approved the human trial after reviewing the available laboratory and animal data.
Vaccine researcher Alex Sampson said: “As soon as we heard there was an outbreak, we were able to scale up really, really quickly.”
Vaccines can normally take up to a decade to research, develop and prove effective, but Sampson said no corners were being cut.
Sampson said: “We’re doing all the same tests that we would normally do, just we’re able to do them in parallel, so it means a lot of teams working in lots of different places around the clock, but we’re still doing everything that we would normally.”
The Oxford/AstraZeneca Covid vaccine was estimated to have saved 6m lives worldwide during its first year of use, and hundreds of millions of doses were administered.
However, its use was restricted in some countries after reports of rare blood clots affecting up to one in 100,000 recipients.
The experimental Ebola jab may carry the same risk, although this has not been established.
Any such risk would be much lower than the threat posed by the Bundibugyo species of Ebola, which kills about one-third of those infected.
Pollock said severe side effects are “very rare” and that researchers had thought “very deeply” about the implications of testing the jab in healthy volunteers. Any potential risks will be explained to participants.
She added: “I want to stress that the Covid AstraZeneca vaccine was given to millions of people safely.”
Three other vaccines are being developed against Bundibugyo Ebola.
They include an mRNA vaccine from biotechnology company Moderna. Messenger RNA, or mRNA, provides temporary instructions that teach cells to produce a harmless viral protein and trigger an immune response.
The International AIDS Vaccine Initiative and US-based Public Health Vaccines are using technology already shown to work against another Ebola species, although this approach takes longer to manufacture.
