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Oxford begins human trials for ebola vaccine

Thomas Britton reports.

The University of Oxford is beginning the clinical trial stage for its new Ebola vaccine, called ChAdOx1 biEBOV.

The new vaccine uses the same viral vector technology that was pioneered in the Oxford-AstraZeneca COVID-19 vaccine, also developed in Oxford.

The trial, being run and overseen by the Jenner Institute, will have a sample size of 26 volunteer patients, between the ages of 18 and 55. They will receive a single dose of the vaccine and will then be monitored and assessed on several occasions over six months.

We can expect the results from the Phase I trial in the second quarter of 2022, with a further trial set to commence in Tanzania by the end of 2021.

The vaccine targets two of four species of the Ebola virus- the Zaire and Sudan species. Between them, they cause the vast majority of both cases and deaths from Ebola, and the Zaire species has a death rate of between 70 and 90%.

It was the Zaire strain that was most prevalent in the catastrophic West African outbreak of 2014-16 that caused over 28,000 cases and 11,000 deaths, primarily in Guinea, Liberia and Sierra Leone.

The ChAdOx1 virus, or Chimpanzee Adenovirus Oxford One, is a weakened and harmless variant of a common cold virus, genetically designed so that it cannot replicate in humans. The use of a chimpanzee virus is so that no human will have any previous immunity to it.

Although there are already two approved vaccines for Ebola, the new vaccine offers several advantages.

Dr Paola Cicconi, Chief Investigator of the Trial, said that similar to the Oxford-AstraZeneca vaccine, the Ebola vaccine “can be rapidly manufactured at high volume for low cost, with storage conditions amenable to use in the developing world”.

These factors are all very important since the main market for the vaccine will likely be in sub-Saharan Africa, and especially the Democratic Republic of the Congo, which is facing a renewed outbreak in the North Kivu region.

This vaccine is also unique in being multivalent – targeting multiple variants of the virus. By being able to target both Zaire and Sudan variants, the vaccine can be used in virtually all outbreaks and therefore governments can stockpile it, secure that it will be useful if a new outbreak appears.

It is also at present a single-dose vaccine, which is more beneficial in crises and severe outbreaks than the two-dose vaccinations which take longer to be effective.

Professor Teresa Lambe OBE, the Lead Scientific Investigator, has underlined the continued importance of Ebola vaccines, saying “sporadic Ebolavirus outbreaks still occur in affected countries, putting the lives of individuals- especially frontline health workers- at risk. We need more vaccines to tackle this devastating disease.”

Dr Daniel Jenkin, who is the Principal Investigator of this trial at the Jenner Institute, has emphasized the novelty of this vaccine: “This disease can be caused by several different species of virus and each of these may require a targeted immune response to offer protection.

“We have designed our new vaccine to target the two species of virus that have caused nearly all Ebolavirus outbreaks and deaths, and now look forward to testing this.”

The Jenner Institute, named after the inventor and pioneer of vaccines, Edward Jenner, is funded by Oxford University along with many partners, including the Ministry of Health, the Bill and Melinda Gates Foundation, the Wellcome Trust and the European Commission.

It supports research into vaccines and other treatments for diseases as varied as HIV, malaria, tuberculosis, zika, and now-famously, COVID-19.

The ChAdOx1 viral vector that is crucial to this vaccine’s effectiveness has been used in several other projects by the Institute- not just the Oxford-AstraZeneca vaccine, but also for vaccination trials against malaria, MERS, and zika virus.

It was in the aftermath of the 2014-16 Ebola outbreak that ChAdOx1 was first used by researchers from the Jenner Institute to try and prepare for ‘Disease X’, a fictional infection that was used to plan for the next serious epidemic or pandemic.

While Ebola was certainly a greater threat in 2014-16 than it is now, with only very few, sporadic infections across remote regions of Africa, this vaccine could help ensure that no major outbreak happens again and that hundreds or thousands of lives could be saved across West and Central Africa.

Image: Global Panorama/CC BY-SA 2.0 via flickr.com

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