In other words, a so-called "leaky vaccine" or a vaccine that lowers the chances of severe illness, but still allows for transmission of a virus, can create conditions that promote the evolution of more virulent pathogens.

For further reading here is a 2015 NIH-funded study that found "imperfect vaccination can enhance the transmission of highly virulent pathogens.". https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4516275/

The chart entitled "genomic epidemiology of novel coronavirus" shows the increase in mutations after the introduction of these leaky vaccines at the beginning of the year.

https://rumble.com/vldilx-nobel-prize-winner-professor-luc-montagnier-says-vaccine-is-creating-varian.html