First trial shows Ebola vaccine safe; provokes immune response

Researchers said that the vaccine is suitable for further testing in West Africa during the current outbreak

The first human trial of a candidate Ebola vaccine suggests it is safe to use and generates an immune response, Oxford scientists say.

"The vaccine was well tolerated. Its safety profile is pretty much as we had hoped," said Professor Adrian Hill of the Jenner Institute at Oxford University, who led the trial.

The researchers said 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) 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 University trial is one of several safety trials of the GSK/NIH vaccine candidate - in the US, UK, Mali and Switzerland - that have been fast-tracked in response to the Ebola outbreak in West Africa, researchers said.

The initial findings are published in the New England Journal of Medicine (NEJM).

As many as 60 healthy volunteers were vaccinated between September 17 and November 18.

Researchers report safety data and immune responses for the volunteers for 28 days after immunisation. Follow-up of the vaccines will continue beyond these initial data until six months after the volunteers received the experimental vaccine.

The volunteers received one of three different vaccine doses. 20 volunteers received a low dose vaccine; 20 volunteers a middle dose; and 20 volunteers a high dose.

The experimental vaccine was well tolerated at all three doses. The majority of adverse events reported by the volunteers were mild in severity.

Two people experienced a moderate fever within 24 hours of receiving the vaccine, but this passed within a day.

"People typically experienced mild symptoms that lasted for one or maybe two days, such as pain or reddening at the injection site, and occasionally people felt feverish," said Hill.

Importantly, the vaccine generated immune responses against Ebola in the volunteers. Levels of antibodies increased over a period of 28 days after vaccination, and there was no significant difference in the levels seen at different doses. Levels of T cells - cellular immunity is the other arm of the body's immune system - peaked at 14 days.

The levels of antibody response are like those seen with a similar vaccine dose in a US study of a related GSK/NIH Ebola vaccine formulation published in November.