In the past couple of days I've dug out the WHO data on SARS, which lists those countries that had some person to person transmission of the SARS virus 18 years ago.

Looking at the Covid cases for each of those countries reveals a high degree of resistance to the bug, the only country having a significant number of Covid cases being Canada. Even then, the Covid infection rate for Canada per 100,000 people is only a third that of the USA.

I'm increasingly convinced that the route to becoming post-Covid is not vaccination with dead virus, but a very light encounter with the live virus, to sufficiently stimulate our immune responses, but without causing an infection.