In theory if enough people have enough immunity you can explain any advantage with immune escape. I can’t rule it out. However, I’m skeptical, primarily because if everyone was previously infected then you wouldn’t see vaccines giving much advantage vs. infection (either by Omicron or Delta) or protection against severe disease. The fact that vaccines or being infected still matters vs. baseline population puts a not-too-high cap on how many people have already been infected, which in turn makes the current doubling times very hard to explain with evasion alone.
In theory if enough people have enough immunity you can explain any advantage with immune escape. I can’t rule it out. However, I’m skeptical, primarily because if everyone was previously infected then you wouldn’t see vaccines giving much advantage vs. infection (either by Omicron or Delta) or protection against severe disease. The fact that vaccines or being infected still matters vs. baseline population puts a not-too-high cap on how many people have already been infected, which in turn makes the current doubling times very hard to explain with evasion alone.