@SW-User In fact, going to / aiming to. This for ChAdOx-1 at least, from what I read, not sure about Moderna's one.
I don't know what I would do if I was on an ethic board myself, there is also to consider that the virus itself spreading uncontrollably could potentially take out (or permanently damage) a lot more lives than the volunteers going through a challenge study, exposed to an attenuated variant of the virus, with a controlled infection dose, in a controlled setting.. :|