> Or are there enough people out there who have been exposed within three days and are as of yet symptom free?
Well that number seems to be increasing every day. So that is a positive um right?
Actually I think the way you do it is with a double blind in a population that is already likely to be exposed, or likely to be exposed soon.... then watch for whether the people vaccinated with the real deal vs the placbo get infected at higher rates.
Since you don't even know if it works, its not like you are actually withholding treatement on those with the placebo, and its a population you expect to have some cases anyway. So if it works, it could protect some of the population and allow for others.... if it doesn't work, any new risks they are exposed to are only from the drug itself, as long as you can weigh that against the risk and outcomes of ebola infection.....
Essentially I think the only viable population is medical professionals themselves who work with Ebola patients, and family of patients who just recently brought their family member to the clinic. That is mostly because any cases that are found have to be isolates asap and so there is no possibility for any real control group outside the clinics/centers.