I believe this was from a 'Dr. Geert' from early March. He is very pro-vaccine, but he was adamant that pushing 'vaccines' in the midst of a pandemic was a great mistake because it would drive the propagation of a multitude of variants. As you said, vaccinated folks become variant factories.
I believe you can find the video on Rumble on 'The Highwire with Del Bigtree' site. March 12th, 'The Coming CoVid Catastrophe'.
I'm sure there are other videos, reports - and maybe more recent - but this is one of the first ones that I saw.
It’s the pool of the unvaccinated that is the variant factory. Aided by whoever started this bioweapon in the first place.