Ebola vaccine trials show positive results

5 February 2015

The first results from a trial of a candidate Ebola vaccine at Oxford University in the United Kingdom suggests the vaccine has an acceptable safety profile at the doses tested, and is able to generate an immune response.

“The vaccine was well tolerated. Its safety profile is pretty much as we had hoped,” said Professor Adrian Hill of the university’s Jenner Institute, who led the trial.

The researchers say these results suggest the vaccine is suitable for further testing in West Africa during the current outbreak, with the aim of determining whether the vaccine offers protection against Ebola.

The candidate Ebola vaccine is being co-developed by the US National Institutes of Health (NIH) and GlaxoSmithKline (GSK), the British multinational pharmaceutical group, against the Zaire species of Ebola, which is the one circulating in West Africa.

It uses a single Ebola virus gene in a chimpanzee adenovirus to generate an immune response. As it does not contain infectious Ebola virus material, it cannot cause a person who is vaccinated to become infected with Ebola.

The Oxford trial is one of several safety trials of the GSK/NIH vaccine candidate – in the United States, UK, Mali and Switzerland – that have been fast-tracked in response to the outbreak.

Between 17 September and 18 November, 60 healthy volunteers were vaccinated at the Jenner Institute. Researchers reported safety data and immune responses for the volunteers for 28 days after immunisation, and follow-up of the vaccinees will continue beyond these initial data until six months after the volunteers received the experimental vaccine.

Importantly, the vaccine generated immune responses against Ebola in the volunteers.

“Whether we have a vaccine that is safe, effective and works, we won’t know for a while yet. But we owe it to the people who have been affected so badly by the Ebola outbreak to find out,” said Hill.

“The results are very encouraging in terms of the safety profile of the vaccine. That is the main outcome from this trial,” he said. “We have seen an immune response in the great majority of people receiving the vaccine. It is possible to be optimistic about the immune responses we’ve seen; it’s also hard to be really confident the levels would be protective.

“Larger trials in West Africa will be able to tell us more. We are also currently assessing another option, involving a booster dose, for improving immune response levels.”

Similar initial results from an American trial in 20 people of a related Ebola vaccine formulation were published on 26 November. Results from trials in Mali and Switzerland are expected shortly.

The Oxford scientists have also begun testing the safety of a candidate booster vaccine against Ebola, to find out whether it could further increase the immune responses.

“The speed at which all this is happening is remarkable,” Hill said. “We’d especially like to thank all the volunteers. They continue to take time out of their busy lives to give blood samples at regular intervals so we can understand more about their immune responses having received the vaccine.

“It’s also thanks to the hard work of many scientists, funders, pharma firms, regulators and agencies, all coming together, that we can make such rapid progress.”

Source: University of Oxford