I disagree with the assertion that vaccination had no effect on viral load. Titers soar up on infection, and that is reflected in modes of transmission. I can generate citations if you’d like, but I don’t think that’s good use of time. Yes, it could be a question of increased virulence, but I’m a big fan of Occam's razor — many of the cases can be traced back to specific ‘patient zero’ situations where an unvaccinated person contracted the infection, then transmitted to others.