It wasn’t that long ago that the scientists were suggesting 70% was sufficient. Is it that >90% is required when the vaccines don’t effectively impede transmission? Is it possible 100% would not be sufficient?
It's been clear for a long time that even 100% won't make the virus disappear. Yes, back in the early days when we didn't use the greek alphabet yet eradication was a reasonably possible best case outcome (though not really likely, given the transmissibility across species.
Look at how prevalent pre-delta variants are now: no, they have not disappeared because almost everybody had delta, they have disappeared because of vaccine shots combined with moderate (compared to 2020) NPI. A virus strain does not simply disappear because there's a new one in town, it keeps replicating until it runs out of hosts. And virions are certainly not defecting to a newer, more glorious flag (like humans might do)
The 70% number was often mentioned when the original variant was still predominant end of last year. Alpha and Delta are just so much more transmissible. The vaccine was never said to prevent all infections by serious scientists
