According to this article to see if the vaccine is affective you need 10,000 people and 13 with the placebo to get infected if so why can’t a simple clinical trial be done in New York State or elsewhere with 10,000 people that have antibodies and a X number who were not infected To prove if you can get reinfected with the virus?
https://www.nytimes.com/2020/04/27/world/europe/coronavirus-vaccine-update-oxford.html
These trials are not just to prove the vaccine immunizes at least x (say 70-90%) of the recipients, see below:
I think the trial with 10,000 people called a stage 3 clinical trial, which they do for 9 months.
They first do smaller stages that are with fewer people and over less time (1-3 months).
The reason they do these trials is:
1. The obvious, to ascertain that the vaccine immunizes a certain percentage of test participants
2. To see if there are any serious/widespread side effects
3. To make sure the vaccine doesn’t cause the opposite of the intended affect, where test participants who get infected with COVID-19 fare worse with the vaccine than those without. This has happened with other vaccines in the past and thus has to be ruled out before the vaccine is widely distributed, so it doesn’t end up doing more damage than good.