Ebola vaccine developers are on track to start testing their products in West Africa in about a month, the World Health Organization said at a press conference today.
And it's a race against the clock — testing will become more challenging if the number of new Ebola cases continues to drop.
Two vaccines have already passed the preliminary safety trials — one from GlaxoSmithKline and a second being developed by Merck and a small biotech company called NewLink Genetics. The next step is to find out whether either or both will actually protect people from this deadly disease.
Testing has been a delicate subject, because the most effective tests involve a comparison group that will not receive an actual vaccine – at least not right away. Some people object to tests like this because they feel they are being exploited as experimental subjects.
But vaccine organizers hope they've found a way to involve West African citizens without alienating them.
Liberia, Sierra Leona and Guinea each have different testing strategies, Dr. Marie-Paule Kieny, Assistant Director-General at the WHO, said at a news conference Friday.
Liberia's current plan is to test both vaccines in a head-to-head trial, and have a third group that will receive a placebo shot. Each of the three groups will include 9,000 volunteers. That test could start as early as the end of January, Dr. Kieny says.
Sierra Leone's trial will focus on health-care workers and others at high risk for coming in contact with Ebola. Kieny says they will test just one vaccine – which they have yet to choose. The vaccine will be tested in gradual steps, so people who are not initially vaccinated will be the comparison group. This study will involve 6,000 volunteers.
Guinea plans to identify 90 new outbreaks of Ebola and vaccinate people in the community where the outbreak is taking place. This strategy was used successfully to eradicate the last cases of smallpox.
"What they did in the time of smallpox is when they had confirmation of a case, they immunized the community of the case, the village, let's say," Kieny said. This stops the spread of disease the way a firebreak – a strip of cleared land — stops a forest fire.
In the case of Ebola vaccine, some people will be vaccinated immediately, while others in the community would get the experimental shot later. Health care workers around the outbreak would also get the injection.
Kieny said this approach is likely to give the quickest answer about whether a vaccine is effective, since scientists can then compare Ebola rates in people who have been vaccinated versus people who were not.
How long this will take depends on how quickly Ebola continues to spread – scientists need to observe enough cases of disease to tell whether the vaccine is having an effect. Ebola is dissipating quickly in Liberia and shows signs of abating in Guinea and Sierra Leone, according to WHO statistics. So it could easily take six months before scientists can say whether either or both of these vaccines are effective.
"Hopefully we will have broken the back of this epidemic by the time we've finished these trials," says Helen Rees, a professor at the University of Witwatersrand in South Africa and chair of the WHO Ebola vaccine committee. So vaccines may not play much of a role in stopping this outbreak. But they could still be useful.
"We anticipate this is not going to be the end of Ebola, that we are going to continue to see sporadic cases that might become more widespread, as we've seen in this instance," Rees said at the WHO news conference. Having a proven vaccine could help prevent another epidemic.