In this study the scientists used crab-eating macaques and protected them with a Ebola virus vaccine on days 3, 7, 14, 21 and 28 days before introduction of the Ebola virus into the animals. What the authors observed with the 3 animals that were vaccinated 3 days before injection of the virus was that one had to be euthanized and two showed symptoms. In contrast the 3 control unvaccinated animals all had to be euthanized. On the other hand all the animals that got vaccinated on days 7, 14, 21 and 28 before virus exposure exhibited no symptoms. This result is remarkable, as even with such a small sample size we are getting near perfect immune response towards a very infectious and deadly virus.
This work correlates well with other human clinical trials that have shown to be safe and immunogenic (i.e. they create an immune response). It should be noted here that obviously the difference between human and animal trials is that animals are knowingly infected, whereas humans are not. As such the human and animal trials are both statistic studies, however with the animal studies we have a precise number on the infection rate.
In my opinion, these two studies show that animal trials while not appealing to the human mind are a necessity at times. If not, we need to consider the only other logical choice and that is using human guinea pigs. Now, I am pretty sure that most people would be highly opposed to the idea of using human patients and knowingly injecting them with deadly viruses such as Ebola. Lastly, I said logical choice earlier as there is another branch of irrationality in the world. These are people that believe we should not use vaccines and not do any drug testing. Often these people die or they lie and get all the animal tested treatment they need. Either way the answer reverts to the only other logical choice if you are opposed to animal testing, if not you are dead and then your opinion no longer matters.