Apologies for digging up an old thread but I found these replies interesting.

I also had scarletina as a child.
I'm prone to cold sores at the drop of a hat, all over my face.
Despite hanging out with the chicken pox kids, I never caught it. I was tested as being susceptible to pox when started nursing (not immune). I had the vaccine and was re tested; still not immune. No natural or vaccine immunity but never had it either despite lots of contact.
Stressful childhood and youth. Never stopped worrying, anxiety and internal conflict most of the time.

finally, my mum's contribution to theories; as a child growing on a farm in the 80's, i frequently drank milk straight from the tank. After the chernobyl incident, we often had testers sample the milk for radiation. we never got results but fallout would have been recycled to rain, grass, cows, milk, me.
Oh and I'm white, female, childhood in wet dark wales.