How much are antibodies present in your sinuses versus your bloodstream or various organs? My layman education here would suggest that antibodies are not really

How much are antibodies present in your sinuses versus your bloodstream or various organs? My layman education here would suggest that antibodies are not really a big factor with the initial infection and spread, only when someone develops a serious infection and is sick enough they probably aren't walking around willy-nilly in public anyway. So that would explain why the vaccine protects against serious illness, but is less helpful in preventing infection and spread. [EDIT: A quick google suggests that, fascinatingly, the mucosal system in your sinuses apparently has its own independent antibody development and production. The vaccines apparently don't trigger antibody production in your sinuses.] Similarly, it might be beneficial if we could train this initial immune response better. I am not sure how it works. I know that despite extreme and very prolonged exposure to a very sick Covid-19 victim, I was unable to test positive for Covid and didn't have antibodies.