My GF, who has severe asthma, had her first jab at the end of January.
A couple of weeks ago on Saturday, despite her having been shielding for over a year, she called me downstairs saying she was not feeling well. We thought it was just another asthma flare up, but called 111 and, having been told her symptoms, they sent an ambulance.
It ended up with her being taken into hospital overnight where they confirmed that she'd contracted COVID-19. (We guess it was from a dodgy packet or food delivery she's had.)
On Friday, we'd been cuddling, on the Saturday, I spent over an hour right next to her whilst she was coughing etc, yet, even though I haven't had a jab yet, I have *not* shown any signs of the virus, even though it would normally be pretty much guaranteed that she'd have been contagious had she not had the jab.
Also she has (especially given her asthma) had a very mild case. Yes, she's been coughing, had a temperature and been tired, but, compared to some of the possible symptoms, she's got off lightly and I've got away scot free.
Now, of course this is only a single example, but it's an interesting data point.
ADDENDUM: When she had the jab, she did have some aches and felt a bit off, but nothing major.