Well, I don't know in general if people think mommy intuition works. Personally, I know mine is right 100% of the time, I just don't always recognize it for what it is.
I had this sense about my dd's 2nd shot. We were already delaying & selectively vaxing, but I just had this sense of dread and anxiety for days leading up to the vax appt at the health unit. I passed it off as me being anxious about her being poked, but decided to only do 1 vax instead of the 3 we'd been planning.

:
The single shot we did was Pentacel - it's the DTaP/HIB/IPV combo vax here in Canada. My dd started screaming immediately and had that high pitched scream that would start and stop all the sudden. Then she went to sleep and wouldn't wake to feed.. her interaction when she did wake to scream wasn't normal, her babbling stopped, she quit pushing up with her lower legs. She was 6 mos old at the time. She got a fever, and 5 days later when we took her in for a check up with her dr, she had lost weight, and it wasn't a difference in scales.
It took her 6wks to regain verbal skills to where she'd been, and it was another 3 mos before she started using her legs again. I knew it was a reaction, but didn't know much more beyond knowing I wasn't going to give her anymore shots for a good long while.
Scarily, I still thought this to be a "normal" reaction, but it was enough for me to research more. And then the diagnosis of hypotonia started getting tossed around when she wasn't walking yet at 18mos. This was the point I put hypotonia and vax reaction into google along with DTaP and got a list of "rare" severe reactions. She'd had every one on the list except for a seizure.

: And that was when I realized fully the severity of her reaction.
I'd already been kicking myself for not following my gut and doing the shot in the first place, all the reactions listed together just made everything fall into place and confirmed that what I had been feeling, I'd been feeling for a reason...
Can I explain it to this day? Nope, no other way to explain it than mommy instinct. And I can say having experienced such a bad outcome to ignoring this instinct, I am much more more in tune with my mommy instincts and am forceful about it if someone challenges me on an issue that my inner voice is screaming about. Interestingly perhaps, it was this lack of inner dread and an inner voice screaming that made me comfortable to not give my 33wk preemie that vit K shot even knowing that he was at higher risk of a brain bleed because of his prematurity... I just "knew" that he was ok and that I'd know it if he wasn't or if he was the 1 in 100 000 that needed the shot.
I think that this mommy instinct is something all women have, maybe some dads too. I just think that society "trains" us to only trust what our eyes and ears can see and to dismiss our feelings and instincts.
That's my thoughts and experiences anyways.