A new Ebola virus vaccine developed by the Oxford Vaccine Group is one of three vaccines recommended for a trial in Uganda to combat the ongoing outbreak of an Ebola variant that evades current vaccines.
Existing vaccines that effectively halt the more common Zaire strain of ebolavirus do not work with the Sudan strain behind Uganda’s outbreak. With support from researchers at the Jenner Institute, Professor of Vaccinology and Immunology at the Oxford Vaccine Group, Teresa Lambe OBE, has developed an experimental vaccine designed to generate an immune response against both the Zaire and Sudan strains of ebolavirus. The vaccine is due to arrive in Uganda this week.
According to Lambe, the outbreak in Uganda “highlights the ongoing and pressing need for rapid responses to prevent outbreaks escalating further”.
Since Uganda declared an Ebola disease outbreak caused by the Sudan ebolavirus on 22nd October, 163 infections and 77 deaths have been reported across nine regions. The urgency of this situation led the World Health Organisation (WHO) and the Ministry of Health in Uganda to co-sponsor a randomised ring vaccination trial of vaccines designed for the Sudan strain. This method was previously successful in Zaire ebolavirus outbreaks in Guinea and Sierra Leone.
The WHO asked the existing COVID-19 Vaccine Prioritisation Working Group to extend its COVID-19 remit to rapidly evaluate the suitability of candidate Ebola vaccines for inclusion in the planned trial in Uganda using similar considerations on safety, likely efficacy and logistic issues relating to availability and implementation.
Consequently, the WHO Vaccine Prioritisation Working Group recommended on 16th November that the Oxford biEBOV vaccine be included in a planned ring vaccination trial in Uganda. Two other vaccines from the Sabin Vaccine Institute USA and International Aids Vaccine Initiative were also recommended for inclusion.
Oxford’s ebola vaccine was developed using methods proven successful in the development of the Oxford-AstraZeneca COVID-19 vaccine. Both share a common vector of the ChAdOx1 virus, a weakened version of a common cold virus (adenovirus) that has been genetically modified so that it is impossible for it to replicate in humans.
The Working Group noted that the Oxford vaccine’s use of the ChAdOx1 platform in the COVID-19 pandemic was tested in the field with over two billion doses. However, they ranked the Oxford vaccine last out of the three as there is limited clinical trial experience with the ChAdOx1 platform encoding an ebolavirus insert.
Sandy Douglas, Associate Professor at the Jenner Institute and lead on manufacturing scaleup for the Oxford vaccine, was keen to highlight that “[o]ne of the key advantages of this [Oxford ebolavirus vaccine] is that it should be possible to produce it at [sic] very large scale”. He noted how the Serum Institute of India was able to use Oxford’s adenovirus manufacturing techniques to make more than one billion doses of the Oxford adenovirus-based COVID-19 vaccine.
Disease outbreaks are unpredictable, and according to Dr Charle Weller, head of infectious disease prevention at Wellcome, the WHO may use only one vaccine in the field to ensure enough data is collected to assess one candidate fully, or decide to use all three in case one fails. The vaccine trial is also dependent on good relations with the local community, but recent accounts from frontline workers have raised concerns about misinformation and local conspiracy theories that claim the Ebola outbreak is fake.