For this trial, the placebo and treatment groups are both composed of healthy volunteers that are exposed to a controlled amount of an attenuated dengue virus (

For this trial, the placebo and treatment groups are both composed of healthy volunteers that are exposed to a controlled amount of an attenuated dengue virus (called rDEN2Δ30). All groups in the trial are told the risks of exposure to the virus. Because the virus is attenuated (weakened), the risk of severe sickness is very very low. The point of using an attenuated virus is that this is a "challenge model" that is supposed to simulate an exposure to the real virus closely enough that one can judge if the vaccine is likely working, without exposing the patients to the risks of infection by the full-strength virus. CNN did a much better job than Wired in explaining this. http://www.cnn.com/2016/03/16/health/dengue-vaccine-effective/index.html http://www.cnn.com/2016/03/16/health/dengue-vaccine-effectiv... Therefore, the fact that the placebo group had certain levels of various symptoms (according to the article, 80% had a rash, 20% had nausea, etc.) is still important data for other scientists who are trying to judge if they should use the rDEN2Δ30 challenge model in their candidate vaccine trials. It's not intended to provide data on what natural dengue fever is like, which I agree would be unethical and unnecessary.