My doctor was an old man (near retirement age) when he vaccinated me the second time. He had also given me my first one. He had lived through a time when small pox was still an active health threat. I remember him telling me that there was very little chance that I would have a second scar. He said that I was more than likely still immune from the first vacination. He said that is was very rare for a person to have a second scar. (I remember this because no teenage girl wanted an extra scar)
My husband was first vaccinated in the early 1950's and then again in the late sixties before a trip overseas . Same story here second vaccination didn't leave a scar. I remember people saying that the second one didn't take.
I remember that one girl in college had two scars and that she was the only one that I ever knew that had two scars.
My parents were both born in 1910, I know that they had been vaccinated long before I was born, either when they were young or as soon as the vaccine was available. Mom took a trip to Europe in the mid 1970's and was re-vaccinated at that time. She had no second scar. She figured she would since it had been so long since her first vaccination.
I know my dad had more than one but I don't know the years on his but again it only took once.
Now not being a doctor I don't know but I have a strong feeling that the immunity may last quite a long time since the second ones never seemed to take. I am hoping that this mini-history may give you some clue as how long and strong the immunity may really be.
See my post#137. I have exactly the same feeling that you have. My last four vacccinations had no reaction at all, but I'll still go for another when they become available.
I am very worried for the unvaccinated young people of today, which includes our son. If an outbreak occurs in my area, the only defense I can think of (prior to exposure) is complete isolation of the family, which would mean staying at home with no contact with anyone or anything, until the Health Department calls everyone in for mass vaccinations.
Thank you bonesmccoy for posting this thread. The information you provided is invaluable and appreciated.