[GavinB]

I agree in principle. On the other hand, global crises have always called for extraordinary measures.

Even in this pandemic, we've (correctly, I would say) basically thrown out important principles like freedom of movement and freedom of association during lockdowns. I think that allowing volunteers to put themselves at a relatively low risk to speed up vaccine trials would have been a relatively small transgression, compared to the lockdowns and travel bans (which, again, I think were justified).

But I do take your point.

[cameldrv]

This is a very good point. The lockdown measures, while very arguably necessary, are an extremely severe measure. They were perhaps the only measure that would have been effective at the beginning when there was no preparation.

Yet, things like enforced mask wearing, or enforced out of home quarantine/isolation somehow were off the table. It is a weird path-dependent quirk of the fact that we had no testing at the beginning, that instead of quarantining and isolated the exposed and infected, we are effectively quarantining everyone.

[raphaelj]

Isn't it exactly what happened? Some vaccines started large scale tests around March/April.

It's just that you have to wait a few months to know if the vaccine you're testing is effective. You can't make this delay shorter with more volunteers.

And when you're fighting a decease that "only" kills 0.5% of the people inflected, your risk margin is pretty low (what if your vaccine creates deadly consequences to 0.6% of the people vaccinated?).

[maxerickson]

Challenge trials shorten the period by intentionally exposing the volunteers to the infection.

The mRNA vaccines had to wait until November to get enough infections.

There can be an issue that the measurement of the effectiveness of the vaccine is then related to the exposure protocol (which may not be the same as typical natural infections), but it's reasonable to expect results much sooner.