It's not really ethical to keep the control group unvaccinated once Phase III was over and the EUA was approved. Ethics aside, the control group would probably leave the trial to get vaccinated anyway.
Just because something is not possible, does not make it any less required.
Yes, it does.
Because that would be like saying, just because all you got is a binocular with very limited magnification/resolving power, satelites for jupiter does not exist, because you cannot see them through it.
Someone should name this fallacy.