Going back to the discussion on challenge trials, I was listening to a Ted talk regarding these and apparently around 40,000 people have already signed up here to participate in covid challenge trials, so it seems perfectly reasonable to think that if governments offered a decent sum of money they’d get a glut of volunteers.
https://www.1daysooner.org/
Also, interestingly, the speaker was asserting that challenge trials only require 50-100 participants. They’d also yield results in around a month. Encouragingly, the UK are said to be organising one such trial for early 2020, although I haven’t confirmed if that’s true or not.