My wife gets her flu jab every year, as she's "clinically vulnerable", having asthma. She never gets flu, so that seems to work.
We both got the first round of Covid jabs, and both got Covid not long after. Wasn't too bad, annoying more than serious. So the jab doing it's job, and keeping the symptoms mild, then?
We both went for the second round jabs, and guess what? Yep, both got it again, a few weeks after. Again, not too serious. Just like a bad cold or mild flu.
Since then, neither of us had a Covid jab, and have never had Covid since.
I'm not Anti-Vax, or any kind of idiot conspiracy theorist, and I'm not suggesting anyone else should follow our example. It's just that in our case, NOT getting the jab seems to offer better protection than getting it.