Hi and Welcome to the board!
I'm sorry to read about the concerns with your son. This must have been hard, especially if it was due to the late shot.
I didn't know it was rare in black people. I'm not even sure how rare it is in white people to be honest!
I'm naturally blonde, so don't fit in with the red hair but have always had low blood pressure and low temp.

it confused the hospital last year when i had a benign breast lump removed. I'm overweight and they thought i should have higher temp and blood pressure... they nearly didn't let me go home, it was only that I asked them to check what I was when I was admitted!
good luck with your book, i'm sure the genearations down the line will appreciate it!
I think i must've got it from my dad, as my mum was a diff blood group to me, I didn't know my dad.
Take care, Jane