As the Ebola epidemic raging in the Democratic Republic of the Congo shows no signs of abating, researchers around the world are scrambling to develop vaccines and treatments to fight it.
Ebola disease is caused by different species of orthoebolaviruses – including Zaire ebolavirus, Sudan virus, and the Bundibugyo virus which is responsible for the current outbreak.
However, the only vaccines and treatments currently licensed for the disease target the Zaire ebolavirus.
Confusingly, this species of the virus is now just called Ebola virus – perhaps partly explaining why so few tests and vaccines are available.
Last week the World Health Organization (WHO) convened experts to review the most promising vaccine candidates against the current strain, and on Monday the non-profit Coalition of Epidemic Preparedness Innovations (CEPI) announced that it was awarding more than $60m funding to fast-track three different shots.
Some aid agencies are warning that the current outbreak – which may have been circulating since January – could be worse than the 2014 to 2016 West Africa epidemic, which infected nearly 30,000 people and killed 11,000.
“Development of a vaccine and other countermeasures, including treatment or other prophylactic agents, is clearly a priority,” said Mark Feinberg, president and chief executive of IAVI, one of the research groups at the forefront of developing a shot against Bundibugyo.
These are the most advanced candidates.
According to the WHO, IAVI’s single dose vaccine candidate currently offers the most promise. The shot is based on an rVSV vaccine platform, which has been successfully used to develop vaccines against other species of Ebola virus.
The latest vaccine has shown almost 100 per cent efficacy in pre-clinical trials on monkeys – the “gold standard”, said Feinberg – as well as generating a fast immune response. And it is the only one of the three most advanced candidates to reach this stage of development.
IAVI, a non-profit research institute that was originally set up to develop an Aids jab, has been granted $3.2 million by CEPI to create the starting material needed to manufacture a vaccine and begin testing.
WHO believes that it is likely to take seven to nine months before it even gets to clinical trials in humans, although Feinberg said he hoped that the process could be accelerated in a “compliant and proper manner”.
“It’s very important that there are multiple candidates being advanced because you never know which one is going to work. But we also recognise that alternative candidates will likely require two doses of administration to get protective immunity,” he said.
This vaccine uses the ChAdOx1 platform, the basis for Oxford University’s Covid-19 vaccine, developed in partnership with pharmaceutical firm AstraZeneca. This formed the backbone of the UK’s vaccine campaign but was linked to rare, and sometimes fatal, blood clots.
The vaccine is being developed in a partnership between the university and the Serum Institute of India, which has broad experience of vaccine manufacturing at scale.
The WHO believes this jab could become available within two to three months for assessment through a clinical trial, although more data from animal studies are needed. CEPI will initially fund up to $8.6 million to help it get to preclinical testing and phase1 clinical trials. According to the WHO a single shot of this jab could be used to protect contacts of people with Ebola but two doses would be needed for those at high risk, such as health workers and frontline responders.
WHO has not made any public assessments of the Moderna shot but CEPI has pledged up to $50 million for preclinical testing and phase 1 clinical trials. If the initial data is promising the CEPI funding will also support the launch of simultaneous phase 2 and 3 studies. This candidate uses the same “fast, flexible” mRNA technology the biotech developed for its groundbreaking Covid-19 vaccine.
Stéphane Bancel, chief executive of Moderna, said he believed the mRNA platform could respond rapidly to emerging infectious diseases. “We will move with urgency and scientific rigour to support the response and help bring a potential vaccine closer to the communities that need it most.”
WHO experts looked at Merck’s Ervebo vaccine developed in response to the West Africa epidemic – however, that was caused by a different species of the virus. The vaccine has since been successfully used to control other outbreaks of Ebola. Researchers have carried out small scale testing of the vaccine against Bundibugyo in animals but evidence of the vaccine’s efficacy is still “limited and inconclusive”, said WHO. The organisation recommended that it should only be used in “carefully designed research settings”.
Chinese researchers have also been looking at a broad spectrum shot and, in a paper published in the Proceedings of the National Academy of Sciences on May 18, they showed that their mRNA vaccine protected against Ebola, Bundibugyo and Sudan viruses in rodents. The lead researcher, Sandra Chiu, professor at the University of Science and Technology of China, told the Telegraph that she plans to test it in larger animal models soon.
CEPI and the European Commission are also funding three separate initiatives – led by Stanford University, Danish biotech Adaptvac, and a partnership between Moderna and the universities of Oxford and Leipzig – to develop a vaccine candidate that could protect against a range of viruses, including Bundibugyo. All these projects are at very early stages of development. However, CEPI said it is exploring whether some of this work could be used with a rapid response vaccine platform – such as mRNA or rVSV – to advance a vaccine candidate now. CEPI is also calling for other Bundibugyo vaccine proposals.
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