January 28, 2015

expert reaction to first results from safety and immunogenicity trial of chimpanzee adenovirus Ebola vaccine

The results of a phase I trail of a vaccine against the Ebola virus have been published in the New England Journal of Medicine. The research group tested the virus on participants in Oxford, and reported no adverse side effects.

Dr Ben Neuman, Lecturer in Virology, University of Reading, said:

“The good news is that the vaccine was safe, and nearly everyone who got it made some kind of new immune response. However, the response was smaller than I had hoped.

“In experimental monkeys and people who have survived Ebola, three parts of the immune system are strongly activated – helper T cells, killer T cells and antibodies. In a real infection, these three would work together to attack the infection from many sides at once.  This vaccine gave a more lopsided response – heavy on the antibodies, but light on the killer T cells.

“These results show that the vaccine has the potential to work, particularly in the people who responded strongly, but I have some doubts about its ultimate effectiveness as the vaccine moves into tests in Africa.

“Another big unknown is how well the vaccine will work in people of African descent – nearly all of the Oxford vaccine volunteers were caucasian. People’s genes help determine how they respond to vaccines, and the greatest diversity and biggest genetic differences among people are found in Africa.

“There are other Ebola vaccines and stronger versions of this vaccine in development, and those may one day be able to fix the shortcomings of this vaccine. For now, the most important thing this paper has to offer is hope – hope that an answer for Ebola is finally on the horizon.”

Prof. Jonathan Ball, Professor of Molecular Virology, University of Nottingham, said:

“The data have confirmed that the GSK vaccine is well tolerated, with only a small number of people experiencing very minor side effects, which is good news.

“The vaccine was also capable of provoking an immune response, although the overall potency of this response was a tad disappointing. The magnitude of the immune responses observed in the vaccine recipients were less than those observed in monkeys that were protected from experimental Ebolavirus infection, but we don’t fully understand what degree of immunity humans require in order to protect them from infection. That’s why clinical trials are important.

“It is possible to boost the immunity by giving a second, different vaccine, at a later date, but this won’t be easy, given the relatively poor health infrastructures available in the worst affected areas. Also, the most likely delivery system that could be used to give this booster is also being used in other vaccines targeting important diseases like TB and malaria, and the impact of any Ebolavirus booster jab on the viability of these other developmental vaccines needs careful consideration.

“Either way, Ebolavirus vaccine trials will not be easy, not least because of the falling ebolavirus infection rate. Whether we get an answer during this outbreak is hard to say, but the identification of an effective vaccine will be useful to help fight future inevitable outbreaks.”

Dr Ian Hudson, Chief Executive of the Medicines and Healthcare Products Regulatory Agency (MHRA), said:

“The MHRA is glad to see the development work of Ebola vaccine progressing rapidly, this clinical trial was one that the MHRA fast-tracked and approved in four working days as a part of the global response to the current Ebola disease outbreak in West Africa.”

‘A monovalent chimpanzee adenovirus Ebola vaccine – preliminary report’ by Tommy Rampling et al. will be published in the New England Journal of Medicine at 22:00 UK time on Wednesday 28 January 2015, which is also when the embargo will lift. 

All our previous output on this subject can be seen at this weblink:

http://www.sciencemediacentre.org/ebola-outbreak/

Declared interests

None declared