Hacker News Reader

(A) Did they have someone with Covid-19 sneeze or cough or spit on them?

(B) Or did the candidate just go about their daily lives afterwards?

Because, unless path A was taken, then this 95% efficacy sounds very misleading.

Nothing is misleading. Half the participants got the vaccine, the rest placebo, before going about their usual lives. Now, a few months later, 95 cases have been confirmed across both groups. Of these, 90 had received the placebo and only 5 the vaccine. If the vaccine didn't work at all, the split would be roughly 50/50. A somewhat effective vaccine might result in a 70/30 split, and so on.

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.

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.

Reply on news.ycombinator.com