That's true. But that's the nature of all influenzas: your immunity is only as good as the last generation of infectious agent. The reason they choose the spik

That's true. But that's the nature of all influenzas: your immunity is only as good as the last generation of infectious agent. The reason they choose the spike protein is because it's a vital component in its current state. So to change it and avoid immunity means covid can no longer infect human cells. The only way around this is to radically change the spike protein AND to miraculously find a new spike protein that works for humans. That's why around 1bn people have been vaccinated, exposed to covid 19 and no new spike protein that circumvents the vaccines has evolved yet. Such a change to the nucleocapsid is much easier to make as it doesn't need to interact with human cells.