Specifically, vaccinated people don’t seem to be producing antibodies to the nucleocapsid protein, the shell of the virus. This means vaccinated people will be far more vulnerable to mutations in the spike protein even after they have been infected and recovered.
It also means the virus is likely to select for mutations that go in exactly that direction, because those will essentially give it an enormous vulnerable population to infect.
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.
There's at least one team working on a vaccine that targets another feature of SARS-CoV-2 that changes less than the spike protein does (the interview I heard called it "the N protein"), which could give us a better long-term way to deal with variants. Although I guess it shifts the selective pressure from spike protein mutations to N protein mutations instead. Can't win! Nature is wiggly.
In this case would a protein subunit vaccine like NovaVax have been a better choice for vaccinating the populace? Or would we then have run into the same issue but with spike?
The number in the UK is lower, because there are more vaccinated people. The vaccinated die at ~20 times the rate of the unvaccinated, but when there are only a few unvaccinated, their share of deaths still won't be 99.5%.