Little story for you OP.
When my youngest DD was in nursery, there was a very heavy cold went around her group. All the children had this really distinctive cough and were off for a few days. DD2 caught it and was poorly for a week, before she bounced back and went back to nursery. I caught it and felt truly shit for a couple of days before it became a normal heavy cold. Then DD1 caught it. Turned out the cancer treatment she completed 6 months earlier had damaged her spleen. Also turned out that the "cold" was actually pneumo - one of the things children are now routinely vaccinated for as a baby.
The guilt, OP.
My tiny 6 year old lay in ICU in a coma, for a week, hooked up to machines, with almost 100 holes in her arms, hands, wrists, legs, feet and groin, from where the doctors tried to get a line into her. I had time to count those holes as I sat by her bedside, while the nurses pumped her tiny body full of drugs to try to keep her alive. It took her six months of pain and utter exhaustion to fully recover.
The guilt I feel at not recognising it sooner, not getting her hospital sooner, not protecting her better, has never left. But when I think about how I might feel if I had CHOSEN to leave her unprotected from that illness, if my actions and neglect had directly lead to her catching meningitis, I'm not sure I'd be able to live with myself.
But hey, your choice, OP. Family tradition.