> Studies show that more than 99% of Americans 40 years and older have had chickenpox, even if they don’t remember having the disease. I'm a little surprised t

> Studies show that more than 99% of Americans 40 years and older have had chickenpox, even if they don’t remember having the disease. I'm a little surprised that the quoted age of most Americans having it is not less than that. The chickenpox vaccine was only authorized for use in the US in 1995 (I was born a bit before that, my siblings after that). That would make everyone 28 or older at least 2 years old before the vaccine came out in the US, which is the most likely age people got it. (Assuming that immigrants in the window of 1988 to 1995 from nations who authorized in that period do not make up a substantial fraction of the present US population).