A health worker Ebola treatment center run by the company of the French Red Cross in Macenta, Guinea
PHOTO :. KENZO TRIBOUILLARD / AFP / GETTY IMAGES
When Western scholars began to lay the real world test bases to end Ebola virus vaccines of last summer, Guinea has been on their list of potential locations. There were fewer cases per week that neighboring Sierra Leone and Liberia, and the patients were scattered over a country the size of the UK with very little infrastructure. At a meeting of experts in Geneva, Switzerland, on October 23, the National Institutes of Health (NIH) presented a test plan for Liberia, while the US Centers for Disease Control and Prevention (CDC) offered proposals for Sierra Leone, but there was nothing for Guinea. "What about us?" Guinean delegates asked, said biostatistician Ira Longini of the University of Florida in Gainesville, who attended the meeting. "You let us out."
Now, in an ironic twist, many scientists say an unusual Ebola vaccine trial is expected to begin next month in Guinea may produce the first and perhaps the only answers on vaccine efficacy . New cases of Ebola in Liberia fell sharply, and began to drop in Sierra Leone, which makes it much more difficult to prove whether a vaccine works maybe even impossible. In Guinea, however, a less intense epidemic has not assigned, perhaps making it "the only country where the trial will be enough power to give an answer," says Adrian Hill, a vaccine researcher at the Oxford University in the UK.
the push to test for Ebola vaccines is accelerating. last fall, an international ethics committee convened by the World health Organisation ( WHO) found that the unprecedented threat acceptable to take the Ebola virus vaccines directly from small phase I safety studies in large phase III efficacy studies, while simultaneously conducting phase II studies. two vaccines are now almost ready to jump in. one by GlaxoSmith-Kline (GSK), contains a chimpanzee adenovirus with a gene that codes for the Ebola virus surface protein. the other, developed by NewLink Genetics but now manufactured by Merck, uses a virus called livestock VSV Ebola for transporting a gene.
How to design studies was the subject of intense ethical and methodological debates. In the end, the researchers settled on very different models for each country. In Liberia, the study will use a conventional randomized controlled trial with three arms, one for each of the two vaccines and a third in which people do not receive. It will target the general population in the capital, Monrovia. The CDC plan for Sierra Leone is to recruit workers in Ebola treatment units; everyone will get the vaccine, but some sooner than others. The trial has yet to choose the vaccine, it will test.
The welcome decline in the cases of these two nations means that testing should include a lot of people to determine their effectiveness. Although NIH now plans to enroll nearly 10,000 people in each arm of the trial of Liberia, the current infection rates mean that about 6 months will take to reach a statistically significant response if the vaccine protects 50% of those who get it, said Ripley Ballou, who heads the project vaccine against Ebola GSK. (One answer would come faster if protection rates are better.)
But the epidemic of Liberia could end in mid-2015, suggesting a model published this week in PLOS Biology . "There is a real risk that we will not have an answer at all to the end of the day," said Ballou. Therefore, in addition to counting the cases and deaths, researchers should investigate the immune responses carefully in vaccine recipients to learn as much as possible of each test, said Claire-Anne Siegrist vaccinologist of the University of Geneva.
Guinea study will present an old vaccine strategy, never before used in a clinical trial, it which can yield results more quickly. Inspired by the worldwide campaign that smallpox eradicated in the 1960s, it is based on a concept called ring vaccination. the researchers will look for people newly infected with Ebola, then try . vaccinating a "ring" of people living around them, most likely their village or neighborhood in half rings, the researchers administered the vaccine immediately to an average of 50 people; they will compare their results with other rings where researchers expect 4 to 8 weeks for the vaccine, says John-Arne Röttingen of the Public Health Institute in Oslo, Norway, who heads the study steering group . (It was designed by a coalition including WHO, Médecins Sans Frontières, Longini and several other academic partners.) Frontline health workers will also receive the vaccine, with no control group.
The vaccine for Guinea trial has not yet been chosen, but "we will start in February, even though it is February 28th at 23:30," WHO is Ana Maria Henao-Restrepo said a vaccine against Ebola meeting at the Fondation Mérieux in Veyrier-du-Lac, France, this week. The study could have answers after 3 months, said Röttingen.
If any of the vaccine works and the number of cases keep falling, targeted ring vaccination strategy to mop up remaining pockets of virus can become the best way to fight against the epidemic, said Röttingen .
"It is a very interesting design of a group of very smart people," says Ballou, who adds that the logistical challenges remain daunting in Guinea. The study will chase the case over a wide area, and it does not have the operational and financial support of major players such as NIH or CDC
Meanwhile, a third vaccine candidate has entered the fray :. a pair of new vaccines used in tandem. the week last, Johnson & Johnson announced that it had initiated a Phase I testing and is also looking to phase III study sites Whether any of the three countries can bear a second large study and that. there will be enough new infections once the vaccines are ready for their big jump-remains to be seen.
Correction (23 January 2015) :. a vaccine trial against Ebola virus in Liberia has not conducted by the NIH, as the story says, but by a partnership between the Liberian government and the United States
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↵ * with reporting by Kai Kupferschmidt and Jon Cohen.
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