Mostly to people that are unvaccinated... If 90% of people were vaccinated r would be less than 1 and there would be no spread.

The FDA application for boosters claims that efficacy against transmission for delta for persons vaccinated when the vaccine became generally available is now 42%. That isn't enough to drop Reff below 1 even with 100% vaccination-- in fact, it leaves delta with an Reff higher than the original L strain had absent vaccination.

"no spread" is R=0. Vaccinated people are spreading it to vaccinated people as well as unvaccinated. Assuming that vaccinated people don't know that they get it we have essentially created a big cesspool for the virus to spread undetected.

Luckily that's a bad assumption because the vaccines are so bad that they aren't even protecting people from getting very ill.

> "no spread" is R=0.

If R<1 the number of infected people continually decreases until there are no cases. This is also why it's important for the US to provide other countries with vaccines.

Okay, but you claimed that "there would be no spread". But that is not true for 0 < R < 1. Can you just admit you misspoke instead of arguing a pointless point?

I didn't say there would immediately be no spread. It is true that if there are no cases there is no spread. It's not like it would take very long...