Scientists may have developed an effective vaccine for the Ebola virus after an experimental immunisation gave monkeys long-term protection from the deadly disease.
Human trials for the experimental jab are underway at the National Institutes of Health in the United States, raising the prospect that the vaccine can be used to help resolve the current Ebola crisis in West Africa.
NIH’s monkey studies show that a single dose of the vaccine can trigger fast protection, but the effect waned unless the animals got a booster shot made a different way, according to research published on Sunday.
It took the tested monkeys five weeks for the immunisation to take effect – which is in line with most other vaccines.
Partial protection is better than none, said Dr Anthony Fauci, director of NIH’s Allergy and Infectious Diseases division. But the goal is long-lasting protection, and so booster shots were also trialled.
The vaccine is made with a chimpanzee cold virus, used as a delivery system for pieces of an Ebola gene. The researchers tried simply giving another dose as a booster two months later, but that didn't work well enough.
They then tried a different approach called "prime-boost." The first dose, to prime the immune system, was that original chimp virus-based Ebola vaccine. But for the booster two months later, they made vaccine a different way - placing the Ebola gene pieces inside a poxvirus that's used to make a vaccine against smallpox. This appears to have worked, with the monkeys staying protected 10 months later.
The World Health Organization says more than 2,000 people have died of Ebola in the latest outbreak, and the crisis is rapidly deteriorating.
See the Ebola outbreak mapped
See the Ebola outbreak mapped
1/7 25 March 2014
This outbreak of the Ebola virus first emerged in the Guéckédou region of Guinea, at a crossroads with both Liberia and Sierra Leone
2/7 31 March
On 31 March the WHO confirmed the outbreak was now international, spreading first into Liberia's northern-most Lofa region
3/7 27 May
The virus spread to Sierra Leone at the end of May - just as agencies were hoping the worst was over
4/7 27 July
In Sierra Leone the virus boomed, and then it spread to Nigeria when the Liberian diplomat Patrick Sawyer flew from Monrovia to Lagos
5/7 9 August
The Nigeria cases sparked fears around the world, and there have now been deaths in Spain and Saudi Arabia involving people who had travelled to West Africa. The numbers of cases continue to rise
6/7 17-20 September
In mid-September, Senegal confirmed its first case linked to the Ebola outbreak, a development the WHO described as a top priority emergency. Numbers of cases continued to grow exponentially in Guinea, Sierra Leone and Liberia, as experts warned they could number one million by January if not contained
7/7 8 October
Two cases of Ebola have now been reported in the US and Europe - the first times the virus has been contracted among health workers outside Africa
The WHO said it will fast-track experimental treatments and vaccines, with the aim of getting results from human trials in November. If the vaccine appears safe and triggers an immune reaction in people, the WHO would look to supplying the shots to health workers in West Africa.
Small animal and human safety studies cannot guarantee that experimental vaccines really work in an outbreak, Fauci said. That's why he emphasizes public health measures such as isolating the sick, quarantine and, especially for health workers, using personal protection equipment.
"Make sure people do what works," he said.
The booster-shot findings illustrate an added complexity to speeding an experimental vaccine into the field. The initial first phase study results would shed light only on that "priming" vaccine made from the chimp cold virus, Fauci said. The poxvirus booster step would be tested later only if scientists decided the initial vaccine was promising enough.
Still, manufacturer GlaxoSmithKline has said it plans to begin manufacturing up to 10,000 doses of the initial NIH-developed vaccine.
Canadian researchers created a similar Ebola vaccine that works in monkeys. Manufacturer NewLink Genetics of Ames, Iowa, said first-stage safety testing in healthy volunteers is set to begin in a few weeks.