The highest rates of mutation have been observed in the immunocompromised, many of whom can't get vaccinated. Add to that the fact that vaccines don't terminate the spread by any means, and there are vast reservoirs of animals and people in the Global South who will never be vaccinated all at once, and the idea that mutations can be prevented by mass vaccination quickly comes into focus as a scientific fairy tale.

It would be nice if Covid was a slow-moving target like smallpox. It isn't.

So we'll update the vaccinations annually like we do with influenza. We can't hope to prevent covid from mutating, it's a game of whack-a-mole that requires a totalitarian state to win at.