From (2/2020) COVID-19, Live Vaccine Possible from Wild Serotype Overlap?,

With that taken care of, Indonesia’s claim of zero  native cases (ABC, First case of corona virus linked to Bali after report Chinese tourist returned positive test). is no more than carelessness combined with wishful thinking.

But is it? If confirmed by more  instances, the explanations are limited to three:

• • • Some people are genetically more susceptible than others.
    • Some groups have cultural practices that protect.
    • There are in circulation, one or more corona viruses with overlapping serotypes.

A widely circulating, yet comparatively benign Omicron, providing it retains a serotype that cross-reacts with earlier strains, could function somewhat like a vaccine. What it lacks in efficacy it could make up with omnipresence.

This was written in February 2020, and proved to be false.  It is now possibly true.