Earlier quoted context omitted.
Generally speaking, experimental drug trials are run first on healthy groups and then in at-risk groups (old, young, those with co-morbidities). From the article, my guess is that they are expediting the sensitive groups trials, but unfortunately there's a lack of technical detail. Source: My partner is an infectious disease specialist and we talk about this pretty much daily because I'm so curious.
But for this disease that's particularly bad because Covid has shown to be worst in 55+, obese, comorbidities, etc... which means that the trials on healthy groups are proving very little, since the virus itself is so much weaker on healthy groups.
Doesn't change the fact that, when you're developing a new drug, you want to test it in a way which will cause the least harm. You don't begin trials with those most at risk for obvious reasons. The primary goal of this phase it to asses the safety of the vaccine candidate.
I'm also unaware of any disease that isn't more threatening to people in relatively poor health.