Researchers are racing to determine whether a fast-spreading variant in South Africa poses a threat to COVID vaccines’ effectiveness.
Of course, you're right, the unvaccinated are a fertile ground for mutations that eventually evade the vaccine.
Unless you have a study that backs up the claim that this mutation phenomenon only happens in people not vaccinated for Covid-19, you should probably stop singling them out. The phenomenon occurs in both.
The thing is that mutations probably occur all the time, most don't provide any evolutionary advantage and probably never get passed on, the fact that something with this many mutations being viable is a bit worrying - equally I think that the evolutionary pressure that vaccines represent is going to result in mutations that work better in vaccinated people - and as a result we'll make better vaccines - one of the great things about mRNA vaccines is that we can knock out new ones really quickly
We do know:
> A new coronavirus variant has been detected in South Africa that scientists say is a concern because of its high number of mutations and rapid spread among young people in Gauteng, the country’s most populous province. “Over the last four or five days, there has been more of an exponential rise,” he said, adding that the new variant appears to be driving the spike in cases. “We can see that the variant is potentially spreading very fast. We do expect to start seeing pressure in the healthcare system in the next few days and weeks.”
https://abcnews.go.com/Health/wireStory/south-african-scient...
So two versions which are sequenced as a certain variant may actually have many differences in practice.
I will also add that there are many variants that just havent hit the news cycle. Iirc there was a gamma variant with higher lethality but was much less transmissible.