What is happening in highly vaccinated countries is the vaccines have given people a false sense of security as the vaccines are not very effective against the delta variant. The are freely mingling without masks and getting hit with the delta variant. In countries with low vaccination rates people are still following distancing and masking protocols which is keeping their numbers relatively low.
There is no variant.
There is no vaccine.
See the link I recommended.
Masking doesn’t help at all either way