071107-N-0775Y-008Ebola, the virus topping headlines for the last 6 months, has been officially stopped in Liberia and Nigeria. Despite its spread slowing down dramatically, global fears and the risk to aid-workers keeps the virus at the top of global watch lists.  Now, an experimental vaccine designed to protect against two different strains of Ebola (Zaire and Sudan), without actually using Ebola whatsoever.

The new vaccine, which just passed Phase 1 trials in the United States and UK  with its results published in the New England Journal of Medicine, is based on an adenovirus chassis carrying surface proteins related to the two Ebola virus strains. This means that the “viral machinery” of the vaccine virus is actually from the far less deadly adenovirus (which, at its worst, can lead to lung damage), but has been genetically engineered to provide your immune system with signals that allow it to be “labeled” and “learned” about as if it were Ebola.

As this combination vaccine passes its first phase of trials, a Zaire specific vaccine which has already been deployed in Mali and several other areas with relative success. Because the West African outbreak is being caused by the Zaire strain, these Phase 2 and 3 studies present what will probably the first line of defense for aid-workers deployed in regions where the Ebola virus disease is still active.

In the trial of the new bivalent vaccine, volunteers received one of two doses. Following that, none of the subjects developed any major health problems, though two ran a brief fever within a day of getting the higher dose. Blood samples from all the participants contained antibodies against at least one of the species or strains, but volunteers who received the high dose of the vaccine made more antibodies against the Zaire-Guinea strain than did those who received a lower dose.

Daniel Bausch, a physician at Tulane University in New Orleans, Louisiana, writes that the immune responses look good, but are difficult to interpret. Researchers do not know what kind of immune response is necessary to prevent an Ebola infection, he says. “Since we don’t know where the bar is, that’s a challenge in interpreting these kinds of studies.” As would be expected with a disease as deadly but reasonably none transmissable as Ebola, there are too few opportunities to check the real-world efficacy of the vaccines.

Still, if monkeys models are anything to go on: these vaccines should be providing those test subjects with an effective protection against Ebola infection, according to Anthony Fauci, director of the US National Institute of Allergy and Infectious Diseases (NIAID) in Bethesda, Maryland.

Although this is good news, it won’t affect anyone who isn’t an aid-worker or living in an area seeing an outbreak. Despite the fact that Ebola is mutating twice as fast in humans as in other hosts, certain viral amino acid sequences remain reasonably conserved due to their integral role in viral reproductive viability and protein folding. Although no vaccine is 100% effective (they tend to top out around 80-90%, with flu vaccines being less effective still), it makes sense to immunize aid workers to improve their general safety when working in effected regions. If you are not an aid-worker or living in an area with an Ebola outbreak: you do not need to worry, and if you are worried you should probably read these 6 things that everyone should know about the Ebola virus.