[blackrock]

This sounds like a terrible way to test the vaccine’s efficacy.

A better test would be to have all the participants walk through a minefield of people with the virus. Breath in all that infected air.

Then run the numbers and see who got infected.

[mansr]

It's the standard method, and I see nothing wrong with it. What you suggest (deliberate exposure) is called a challenge trial. This is normally considered ethical only when an effective cure (e.g. antibiotics) is available. Even so, there are plans to conduct such a trial in the UK, and there's no shortage of volunteers. We'll see if they get approval.