Amanuensis

Variants have been one of the hallmarks of this pandemic, with ever more infectious forms of the virus apparently mutating themselves into existence at regular intervals.

… At the point that it was clear the vaccines weren’t sterilising, the theory behind what might be the ‘correct’ level of vaccination changes completely. With non-sterilising vaccines, ‘herd immunity’ becomes impossible and this goal should have been dropped immediately. But worse than that, the fact that the vaccines weren’t sterilising meant there was a large selective pressure for evolution and a sufficiently high viral ‘population’ in vaccinated individuals, and so this also meant that the virus could more effectively evolve vaccine escape.