They lower your chance of getting covid by about 50% if exposed and lower your chance of spreading it if you get it by about 50%. So.. It's not perfect at stop

They lower your chance of getting covid by about 50% if exposed and lower your chance of spreading it if you get it by about 50%. So.. It's not perfect at stopping transmission but you can see how it would definitely reduce the R0 enough to prevent outbreaks in the non-vaccinate pops.