lunchstealer wrote: ↑12 Mar 2021, 19:30
thoreau wrote: ↑12 Mar 2021, 16:55
I would also support challenge trials. While I think they might only buy us a few months in the more plausible scenarios, a few months would still be valuable.
But there's no way America's professional classes would allow challenge trials for anything the public would ever hear about. Too many people would get queasy, so they would only ever use them for stuff that people should get queasy about and would hence never hear about.
Would challenge trials have really shaved off the necessity for Phase 1 and Phase 3 trials? The broadness and length of the Phase 3 trials was kind of necessary to determine how safe the vaccines were, in addition to how effective they were. Challenge trials might shave something off the effectiveness portion but not off the safety portion which requires a reasonably long observation of a large sample size. Seems like maybe you gain a month or two but even that doesn't seem guaranteed.
Challenge trials definitely couldn't eliminate Phase I, where you just see if the vaccine is safe to administer.
A Phase 2 challenge trial would presumably look for effectiveness in a small sample. The test of effectiveness would be shorter, because instead of following people and seeing if they come down with COVID in the course of ordinary life (and it could take a while before they've been exposed) you just expose them after the vaccine has had a few weeks to take effect. It could definitely speed that up.
What we wouldn't know after that Phase 2 challenge trial, even a large one:
1) How long does the protection last?
2) Does it protect people who aren't the more-or-less healthy sorts you could plausibly use in a challenge trial?
Even if Phase 3 were conducted as a challenge trial (which it really shouldn't be if you want to evaluate safety in a larger population that includes people who aren't terribly healthy), a phase 2 challenge trial could justify vaccinating more healthy young volunteers, especially from "essential worker" categories. That probably would have made a meaningful difference in the spread of the virus, if healthy young workers interacting with lots of other people were protected and unlikely to transmit. (Yes, I know, we don't have ironclad data on transmission yet, but humor me here. At the very least, it would cut transmission somewhat, and bring down R0.)
Meanwhile you could do a robust Phase 3 to determine whether this vaccine is worth the resources needed to get it to the general public.
Best case scenario: Phase 3 starts a couple months sooner. We get wider approval in October instead of December. A substantial fraction of essential workers have already been vaccinated when the large-scale roll-out starts, so we're another month ahead of the game. And we've reduced the number of deaths in the interim by tens of thousands, if not more.
I'd say it would be worth it, and not just in the libertarian ethical sense of "The volunteers consented."
But getting people on board with challenge trials? Yikes.