Because the effectiveness of vaccines fade with time, it is a curious fact that having a very fast roll out of the vaccine against 'alpha' may have made us more vulnerable to 'omicron', because we had more people with a 'faded' level of vaccination. That is why the boosters are so important, of course, but it also shows the 'the fastest roll out in the world' may not be as great as you might first think. This is not to say it was anything but a good idea, of course.

That's the trouble with biology and medicine. It is more complicated than it first appears.