Ebola: Don't rely on vaccine to curb epidemic this summer, say drug firms

One expert says aim was to immunise frontline healthcare workers and other first responders in West Africa by January

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Drug companies are warning that a vaccine to protect people against Ebola is unlikely to be ready early enough to curb the current epidemic raging across West Africa, but one expert dismissed suggestions that this represents a failure by the pharmaceutical industry.

“The Ebola vaccine won't be ready for full population immunisation by next summer. That is true. But that was never an objective,” said Professor Adrian Hill, director of the Jenner Institute at Oxford University, which is working with GlaxoSmithKline (GSK) on testing a prototype Ebola vaccine.

“The aim is to immunise frontline healthcare workers and other first responders in West Africa by January with many thousands of doses, not the population with millions of doses. This will be done while data is collected to tell us whether the experimental vaccine works, and how well it might work,” Professor Hill said.

“Vaccine development normally takes 10 or more years. To be able to go from the first safety trials to testing whether a vaccine works and actually using it to help control an outbreak of a horrible disease – all in the matter of weeks and months – that would be something to celebrate,” he said.

Safety is one of the main reasons why a vaccine against Ebola cannot be rolled out soon. It comes down to the inherent risks attached to injecting an unproven medication into the arms of healthy people.

Unlike drugs, vaccines are about preventing an infection rather than treatment, and that means giving them to people who are not ill. Drug companies have to be as sure as they can be that healthy people will not be harmed by an unsafe vaccine.

Ensuring safety normally involves many years of research, first on laboratory animals and then on human volunteers as part of the earliest of three stages of clinical trials. Once safety is established, the vaccine’s efficacy or ability to protect against infection can be assessed more accurately later, larger trials.

Two vaccine “candidates” are currently undergoing phase-1 safety trials. Although they are being rushed through, the results will not be ready for several months and bigger, phase-2 efficacy trials are only likely to begin next year at the earliest – which will almost certainly be too late for the current Ebola outbreak.

Other candidate vaccines are still as the stage of testing on animals. One is funded by the US Department of Defense, which took an interest in Ebola when it was considered a possible biological agent in a terrorist attack.

This vaccine has undergone trials monkeys and has this week received nearly $6m in funding from the US health department to take it to the next stage of phase-1 clinical trials.

One of the two candidate vaccines already in phase-1 safety trials is being developed by GSK in collaboration with the US National Institute for Allergy and Infectious Diseases near Washington. The vaccine candidate is currently being injected into the arms of 60 healthy volunteers recruited by the Jenner Institute, which has many year of experience in vaccine testing.

The GSK vaccine, known as cAd3-ZEBOV, is made from a common cold virus – called an adenovirus – that infects chimpanzees. The virus has been genetically engineered to contain a single Ebola virus gene designed to produce viral proteins or “antigens” to stimulate immunity.

The second candidate vaccine, developed by the Public Health Agency of Canada in Winnipeg and the NewLink Genetics company of Ames, Iowa, uses an attenuated or weakened version of another animal virus that infects domesticated livestock, which again has been engineered with an extra Ebola gene to stimulate the immune system of vaccinated people.

Ana Nicholls, a healthcare analyst at the Economist Intelligence Unit, said that in an epidemic crisis, such as the current Ebola epidemic affecting West Africa, it is possible to cut corners to speed up the process of validating a candidate vaccine – although safety is still a priority.

“Vaccines are, after all, going to be used on large numbers of people who are currently well, which means the standard of proof for safety and effectiveness is higher. That is why GSK is right to say that the vaccine it is developing is unlikely to have any effect on the current outbreak of the disease, always supposing that comes under control soon,” Ms Nicholls said.

The first volunteer on Oxford trial was injected with the experimental vaccine on 17 September and all 60 volunteers will have received their shots by the end of October, said a spokesman for the Jenner Institute. The vaccine is also being tested on a similar number of healthy volunteers in The Gambia and Mali.

If there are no obvious side-effects, yet a strong immune response to the virus, the candidate vaccine could be used in the field. GSK has already stockpiled several thousand doses of the vaccine so that could be used on front-line health workers dealing with Ebola patients if the decision is made to carry out experimental vaccination.