How have they?
COVID - in the vast, vast majority of people - is nothing worse than a bad cough or fever.
In some people, it knocks them sick for much longer.
Some of those people need hospital.
Some of those people need ventilators.
Some of those die.
The vaccines - across all of the above categories - are 100% proven to significantly reduce severe illness. That covers those last three categories, at the very least, and probably gives a significant chance of reducing people getting sick (but not needing hospital) for a sustained amount of time, too.
So then, the illness becomes like any other respiratory illness. It's here, but we live with it. We can't eradicate it, but every year there'll be booster jabs (this has already been said by the powers that be, and I believe it's now Pfizer's main focus??) to target people who are most likely to be at risk to new variants.