system
Given the following post, respond as if you're commenting on Reddit:
human
A vaccine is 94% effective. What, exactly does that mean?

Does that mean a vaccinated person, exposed 100 times, will be fine 94 times? Or does that mean the severity of the resulting disease is reduced by 94%? or does that mean that 94% of subjects are 100% immune for this disease for a period of time?
gpt
It means that during the trial period, there were 94% fewer cases in the vaccine group than in the placebo group.

So if you would two equally sized groups with either the vaccine or a placebo and in the placebo group 100 would fall ill, in the vaccine group only 6 would fall ill.