Also, remember that selection bias still exists. There are going to be individuals with replication but lower viral loads that never get tested because they have no symptoms, and there will likely be a higher proportion of those in the vaccinated group.
There are a growing number of reports of people with breakthrough infections who are experiencing symptoms that aren't "mild", and some reports of people with "long COVID" like symptoms. It's not reason enough to panic, but it's concerning, especially in light of the fact that until very recently, health experts and the media kept telling us that breakthrough infections were "rare" even as it was becoming evident they weren't.
If you really want to embiggen the problem, ask yourself how many people got covid but never got tested. The rate of mild infection is probably a lot higher than reported because only people with anxiety and/or serious covid bothered to get tested or hospitalized. Everyone else called in sick or didn't know/care.
Disclaimer: I'm drunk.
Probably once the initial rush of antibodies dissipates, the virus can get a foothold in the sinuses easy enough. But most the time the immune system will squash it without much trouble.
My feeling so far seems if you think of infection as a continuum then vaccines probably reduce detectable by PCR infection by 2/3rds. Symptomatic illness by 8 to 1. And serious illness by 30 to 1.
But the risk from community spread can be high enough to overwhelm those odds. Where I live case rates are 25 higher than they were 8 weeks ago.