Contrary to media reports, the Omicron was first established in South Africa in just 4 people. They were all fully vaccinated.
How then did this apparently highly contagious variant make its way to Australia (where no one was allowed in or out) and other countries like Wales, within just a couple of days of it being reported? If there was such a variant, it very likely mutated in the vaccinated, which is why so many people developed Omicron just after their latest jab and particularly from the booster shot.
Source: Presidential (Covid-19) Task Force, Republic of Botswana