I’ve heard discussion of this point on a podcast recently. Phase 3 of the virus trial is to administer the vaccine to 10’s of thousands or more people but to also give some people a placebo to create a control group. Then the trial administrators need to wait and see how many of the people who got the real vaccine versus the placebo in order to conclude whether the new vaccine is effective with large numbers of people.
A more direct way to challenge the vaccine effectiveness would be to vaccinate, then deliberately expose the vaccinated person to the virus. This, of course, would never pass an ethics test.
So that means that the trial must wait for the active group and the placebo group to naturally expose themselves to the virus. Conducting the trial in communities whose infection rate is high promises to bring the trial to a conclusive end sooner.
Seems like a weird proposition to me. You don’t want to encourage participants to engage in risky behavior but doing so would help hasten a conclusion that promises a breakthrough for community health.
The college age population, I suspect, will yield results quickly. There’s a hazard that a college student given the placebo might risk more social interaction thinking they have been given the actual vaccination. Tricky business!