It completely makes sense that the potential super spreaders (public facing workers) becoming immune immediately cripples disease spread. I was concerned with COVID19 when it first appeared, because the first strain was much scarier than the other 6 strains.  Now we have what I believe GH strain, which has an R0 6 times higher than other strains (likely above 10), but seems to be much lower danger to people.  And we have treatments we trust.  So we have a situation where the virus is spreading very quickly, but isn't actually doing a whole lot of damage or is even noticed (because no symptoms).