It might be obvious to many in the medical field, but it had me wondering when reading about the new trials for the Oxford-AstraZeneca vaccine that is currently being tested on a group of people.
When you give a group of 10,000 people the vaccine or placebo, do they actually get exposed to the virus or is everything just based on statistics, i. e. assuming that some of the participants will eventually become exposed to the virus by chance?
The fact that a forced exposure would leave both (especially the participants with the placebo) at risk, leaves me to believe that it is not done this way, but then wouldn't a group of 10,000 be far too small?