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An experimental Ebola vaccine seems to confer total protection against infection in people who are at high risk of contracting the virus, according to the preliminary results of a trial in Guinea that were announced today and published1 in The Lancet. They are the first evidence that a vaccine protects humans from Ebola infection.
We believe the world is on the verge of an efficacious Ebola vaccine," Marie-Paule Kieny, the World Health Organization's assistant director-general for health systems and innovation, said during a press conference in Geneva, Switzerland, today.
The results also have implications for outbreak response in general. "This is illustrating that it is feasible to develop vaccines much faster than we’ve been doing," says Adrian Hill, a vaccine scientist at the University of Oxford, UK, who is involved in testing a different Ebola vaccine. “We just need to go on and develop them and get on with them before outbreaks appear.”
An estimated 11,280 people have died during the current West African Ebola epidemic, according to WHO data as of 30 July.
Ring strategy The Guinea trial — called ‘Ebola, ça suffit' in French (‘Ebola, that's enough’) — tested a ring vaccination design, a strategy that was borrowed from successful smallpox eradication efforts in the 1970s. After one patient contracts the disease, their close contacts are vaccinated in the hope of stemming the onward spread of the virus.
The Guinea trial included two arms: one in which adults who had been in contact with someone infected with Ebola and their subsequent contacts were vaccinated shortly after the original patient developed Ebola, and a second in which contacts instead received the vaccine three weeks later2. The trial tested a vaccine called rVSV-ZEBOV, which is composed of an attenuated livestock virus engineered to produce an Ebola protein. The vaccine was developed by the Public Health Agency of Canada and then licensed to the drug companies NewLink Genetics and Merck.
Of the 2,014 people who received the vaccine immediately as part of the first arm, none developed Ebola ten days after getting the vaccine. The 10-day window allows the vaccine to summon an immune response and accounts for any pre-existing Ebola infection. (A few people in the immediate vaccination group, however, did develop the disease between 1 and 10 days after vaccination.) That compares with 16 infections among the 2,380 people in the second arm.
The findings mean that the vaccine provided 100% protection from the virus, though the study's small size means that the vaccine’s true protection rate may be slightly lower, Kieny says. The authors of the paper put its true effectiveness at between 75% and 100%. Hill describes the results as “excellent". "This vaccine works very well for three weeks. That’s good news for an outbreak situation," he says. However, it remains to be seen how long the protection against Ebola lasts. "Will it work at six months? This trial doesn’t tell us that. That’s the next stage," he says.
Immediate vaccination The results come from data up to 20 July, but Kieny said that no new infections have since been detected in people who got the vaccine immediately. On the basis of these results, she said the delayed vaccination arm would be ended, and all contacts would receive the vaccine immediately. Adolescents and children are now also likely to receive it.
Guinea's outbreak is waning — just 4 cases were detected in Guinea during the week of 26 July — but Kieny said that the rVSV-ZEBOV vaccine should help to bring the outbreak to an end. “We will continue as long as there are cases,” she said.
Health officials began vaccinating patients in Guinea in April 2015, when dozens of patients there were still being diagnosed each week. At that time, Ebola was all but gone from Liberia and cases were down drastically in Sierra Leone, the two West African nations where different Ebola vaccine trials were being planned.
With case numbers waning, many experts saw the Guinea trial as the best hope of determining whether an effective Ebola vaccine was even a possibility. The ring vaccination design it used was more likely to return a statistically meaningful result, compared with other trial designs now being conducted in Liberia and Sierra Leone, because the patients enrolled in the Guinea trial were at a high risk of infection.
A vaccine that didn’t exist in the clinic a year ago has shown not only to be effective in a phase III trial but to control an outbreak, which is a fantastic result," says Hill. (Phase III is the stage of a clinical trial which determines whether a vaccine works and is generally required for regulatory approval.)
“This trial dared to use a highly innovative and pragmatic design, which allowed the team in Guinea to assess this vaccine in the middle of an epidemic," said Jeremy Farrar, director of the Wellcome Trust in London, which helped to fund the trial, in a statement. "Our hope is that this vaccine will now help bring this epidemic to an end and be available for the inevitable future Ebola epidemics," he said.
Stockpile excitement In the wake of the trial results, the WHO has decided that the rVSV-ZEBOV vaccine will continue to be used in the current outbreak in Guinea as part of the clinical trial, Kieny said in the press conference. She also said that the WHO is now considering whether to approve the vaccine for general use. That could set the stage for establishing stockpiles to quell future outbreaks — which have tended to flare up in remote communities — and perhaps even for use in this epidemic, should the case numbers in Sierra Leone or Liberia flare up again.
“From a public health point of view, this is a really, really exciting finding,” says Seth Berkley, chief executive of Gavi, the vaccine alliance in Geneva, Switzerland, which funds vaccine access in low-income countries. His organization previously announced that it would pay for production and roll-out of an Ebola vaccine during the current outbreak, should one become available.
He notes that rVSV-ZEBOV is a 'first-generation' vaccine that is not ideal for stockpiling: it must be stored at –80° C and it protects against a limited number of species of the Ebola virus. He says that Gavi will work with researchers and industry to support the development of second-generation Ebola vaccines that target other Ebola virus species, as well as the closely related Marburg virus, and which do not require storage in expensive, laboratory-grade freezers.

The Philae comet lander has not spoken to Earth since a link-up through its parent spacecraft, Rosetta, on 9 July — and scientists may never hear from it again.
But a haul of seven reports analysing data that Philae collected and sent home over three days in November last year, before it went into hibernation, has revealed further puzzling information about the comet it sits on, which is whirling closer to the Sun. Some scientists say the findings suggest that the comet is not an unaltered time capsule from the dawn of the Solar System, as researchers had presumed.
It seems like the more we know, the less we know,” says Geraint Morgan, a co-investigator on the lander’s Ptolemy instrument and a physical chemist at the Open University in Milton Keynes, UK. “The comet is more complicated than we might have imagined.
The hard problem
One puzzle is that the surface of comet 67P/Churyumov–Gerasimenko is much harder than scientists had expected, according to papers published in Science on 30 July. When Philae landed on 12 November 2014, it bounced, grazed the lip of a crater, and bounced again before coming to rest. Measurements of how its legs compressed as they hit the comet1, as well as data from a hammer on Philae2 that tried unsuccessfully to penetrate the surface, show that the comet has a strong, hard crust, covered in places by a softer layer of dust and ice.
That finding could change future lander design, says Stephan Ulamec, project manager for the lander at the German Aerospace Center (DLR) in Cologne. Before the mission, some had feared that the lander might sink into several metres of soft dust. “In the future one would have to think about a mechanism that can cope with pretty hard material,” he says.
The hard surface could be the result of ice grains either compacting or crystallizing under solar radiation. Comet simulations in the 1990s showed that these processes were possible, says Karsten Seiferlin, a planetary scientist at the University of Bern and a member of Philae’s hammer team.
That the comet could have changed since its formation has implications for the wider mission, which had assumed that such bodies had existed largely unaltered since the start of the Solar System, says Seiferlin. But both the hard crust and a large variety of surface materials and structures found on the comet could be the result of recent modifications, he says.
For instance, an intriguing polymer found in the dust3 — called polyoxymethylene — may form when sunlight hits the comet’s surface and triggers reactions that link simple formaldehyde molecules into chains, researchers suggest. If the polymer covers much of the comet, it could explain the object’s dark colour, says Andrew Morse, a member of the Ptolemy team and a planetary scientist at the Open University. The polymer may also be masking signals from other interesting compounds formed earlier in the comet's history, he adds.
“It means we have to understand the physics and processes going on if we want to draw conclusions about the history of the Solar System,” says Seiferlin.
Rugged landscape

For the last few years, Wangda Dorje and Tshering Choden have been the public face of HIV/Aids in Bhutan. They were among a group of five who were the first in the country to come out as HIV-positive - in front of the King, and then on national television.

Wangda Dorje and Tshering Choden have four young children. It's summer in Bhutan, and the sounds of a city under construction, come clattering in through the windows of their two-room flat in the capital, Thimphu. In the kitchen, their 12-year-old daughter is washing up, while the younger children play tag in the tiny living room. The TV is on and the flat is spotless. They seem like a model family, but their lives have been far from ordinary.

It all began in 2006 when Choden was three months pregnant with her second child. She and Dorje were on their way back from hospital, where they had just had a routine pregnancy check-up, when Dorje's phone rang. It was the hospital asking them to return urgently. Not knowing what the matter could be, they quickly made their way back. They were shown into a bare white room with a table and four chairs. Two hospital counsellors, a man and a woman, sat silently looking at Dorje and Choden without uttering a word. "For some time they actually looked at each other, as if they were in too much pain to tell us what they had to say. Then, quite abruptly, the male counsellor asked my wife to go outside," says Dorje. "Then I was really worried. My pulse was racing.
Once Choden had gone outside, the counsellor told Dorje, "The HIV is very active in your body and also your wife's." Dorje looks pale, the shock visible as he recalls this life-changing moment.
"I couldn't speak a word for some time. I was completely lost. Then finally, after some time, the only thought that came to mind was infidelity," he says emphatically, staring at me directly. "I immediately suspected my wife of being unfaithful. Anger rose up so quickly, I felt hurt and furious." But Dorje then asked the counsellor who was infected first, him or Choden, who was then just 18. He replied: "By looking at the body immunity level it looks like you were infected a long time before your wife.
That changed everything. Dorje shakes his head. "I felt really emotional, guilty and sad." He pauses. "Then the counsellor called my wife back into the room. I couldn't bear to look at her face, she was so young.
I was very shocked, I was trembling all over," says Choden. "I couldn't say anything, I was on the verge of crying. And because I was very young, I thought I was going to die. Dorje had been a drug user in his late adolescence, after a failed relationship. It was then that he had contracted the disease through shared needles. He had not even known that this was possible until the doctors explained it to him.