Basically 85% of any given population is the projected ideal percentage to be able to hit, with some degree of confidence, a version of herd immunity thanks to vaccination. So be that business, school, town, state, county, country, etc., etc.; just think that 85% is the ideal. Though anything above 70% is pretty great, and once you get above 75% you're likely going to be set. 85% is the ballpark "magic number" to feel really good about things being about as close as you can get to totally under control without actually hitting 100%.