Growacet - I am very curious about these vaccines as well.

I have tried to find info on how they figure out how affective they are without much luck.

My question is this - if they tested the vaccine on a certain population - some real, some placebo, how do they know it was 95% effective?
They did not inject the participants with Covid 19 and 96% did not contract the disease.  

They did not put them in a room with 1 hundred people who had Covid 19 to see if they would contract the disease.

They sent them back to their daily lives.

So, if someone went home and never left the house - the vaccine worked - becasue they were never exposed.

The vast majority of the population has not contracted Covid without a vaccine.

I have gone a year now with no vaccine and no covid - so, is no vaccine 100% effective?

I am not being sarcastic.  I really want to know how they come up with the vaccine's efficacy rate.