We already have a great deal of pre-existing immunity. The big question we're answering right now is whether vaccine-based immunity (which we have more of in AU, UK, and the US) is as robust as immunity from infection (main source of immunity in SA). It's still too early to say with certainty, but it's looking like the vaccines are working if you're not immunocompromised.

Seems that we don’t have much choice in the matter so we will find out pretty soon. That wouldn’t be the worst outcome.